Spencer Buffalo Model 44, Model 7 Construction, Use And Care

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NITXCROSCOPE

CONSTRUCTION,

PUBLISHED

SPENCER

LENS

BIJFFALO,

USE

AND

BY

COMPANY

N.Y.

CARE

THE

CONSTRUCTION,

AND

CARE

of

the

MICROSCOPE

A

brief outline

optical

special

SPENCER

of

the

principles

referencc

manipulation

PUBLISHED

LENS

BUFFALO,

mechanical

involved,

to efficient

BY

N.Y.

USE

and

with

COMPANY

Copyright r9z6

by Spcocer Lcns

Compaoy

HE

importance

microscope
necessity,

instrument

only

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treatise

working

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alcohol on lacquered parts

alcohol

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modern

built than

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instrument.

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pillar

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proof.

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as illustrated.

parts

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remedied

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holes for

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conical axis

necessary previously

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body of

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careful

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bearing and

l,'is.

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B

these

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by tightening

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the nut

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usually

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of

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C

loose

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or

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Adjustment.

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stand. No high

proper

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ment

no

surfaces should

fect,

always responds immediately

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other

oil

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On all Spencer micros<:opes oil

bearing surfaces to hold

cant.'l'his

be accomplished in any

Body

Tube,

rvhose bearings

are

controlled

The Fine

fine adjustment

power

functioning.

bearing which

in a line at 90o from

Adjustment

is the vital

work can

One of

the essentials

permits

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a free up

plane

lateral motion. The metal

of such

be

texture,

and the lubrication such

bearings should

foreign matter,

which will not become

these, or any other,

become

gummed,

chloroform, and re-lubricate

insures a smooth movement

protected

be

should

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gummy

clean them

reserve

&

other

way.

part

of the microscope

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forming

the fitting

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to

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be lubricated

and sticky.

with

grooves

supply of

ff, when working the fine adjustment

while the

to move

is not central,

fine

the

sists,

fitting,

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occur.

t0

eye

is at the eyepiece,

sidewise, the

or there

adjustmcnt

the :rpparent movement

light

the trouble is in the fine

decided lateral thrust in

a

bcarings.

light coming

is a lateral movement

the object

If upon carefully

of

adjustment-either poor

the mechanism pro-

both.

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movement

by the

Coarse

without its

perfectly

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and

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with

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per-

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with

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up

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dust and

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the

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mirror

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ofr

white vaseline.

from the

in

centering

the object

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per-

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not

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well

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in

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fine

newer

side

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whole

-later

on

micrometer

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adju.stment

with

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the

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two

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arm

and

the

arm

b_e_ of

for

extreme

in

mechanics

in

contact

with

the

two

classes

micrometer

head

two

fine

arm.

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replacing

types:

mov('s

tr'is.

on

better-rvhere

actuated

screw

by

(Figure

D

supplying

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screw

with

lever.

of

*ill

l,ith

its

nut;

fine

adjustments:

the

impulse

delicacv

"""o*plish

a sufficient

especiatty

thleads peipendicular

at

the

to|

oi

adjustment

latter

the

former.

the

one

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the

intermecliate

a lever

E).

heads,

is

the

(Figure

in

connection

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more

Of

the former

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must

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*t

the older

and

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on

convenient

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where

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slicle

with the

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number

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the
the

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the

and

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to see that

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do

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these threads

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into the hollow

position.

it fall into the

removing
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thread

is not noticed

spond. As

top

Most

class

either side

more complicated,

cal

The bearings

are on
alignment
is this
are
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tion

are a
through

and very durable

is entirely

of the arm

of the modeln

where

principles.

cither

accomplished

one continuous

in

as

with

goodly number of threads always

t2

provided

prevent

micrometer

careful in

the

Sometimes

they are

Do not force the threads

help to

are left

see that the

end of the micrometer

Should

it

mechanism

the nut

pin

the

until the

stated above

to replace the

the trvo

of the

for the

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for

in the

360"

other

lever

the

of each thread,

at the

fine threads being removed

threads

replacing these

started straight, and

know

handed. Care should also

little

lost it

be

N at the top

out

drops

out of

arm.

hence the need for the

of

free turning of the shaft. In

lateral

its

fine adjustment does

remove the large

microscopes are of the second

firre adjustmcnt

'I'he

shaft connecting the two

the arm and

as well as where the two bearings

piece

class

stands out as

movement.

end of the

nuts

these

are removed. When this

micrometer

are forced off,

very fine threads

that they

if they

on most

that

pin

P, which

must

it

be

can be

of

before

trearings,

pin.

mechanism

should

passing

micrometer in conjunc-

the

superior. Here there

insuring a steady, regular

microscopes

fits loosely

screw, is

replaced. Should

secured

the

only

arm. In some

the micrometer

and the defect

not re-

nut at the

heads

here is slightly

through

one on

are

best mechani-

precise

in

be

no

the arm.

fully engaged

When this

steady

from

go

be

by

heads

way

at

in

impulse
bell

of the

uprvard
create an

construction

parts

keeps

sible

there may

use.

is applied to the

lever, it

crank

shorter arm to

without

apparent side

together with

all

of

lost

motion

See Figure F-or

be

Fis. H Fig.

generates

any tendency

is such that

a compression

parts

these

is automatically

the slightest

Fis. F

end of the longer arm

reduced

a

upward

move the intermediate slide

move

to

movement of the object.

weight

the

such contact

G,

in

a

B

taken

through long continual

wear

somewhat

it sidervise

of the

spring continually

up even though

simpler form.

Fig. G

moving

that any

A

I

of

thrust

to

The

pos-

a

Figure
similar
thread

of a

of

arm

case

adjustments
ping
has

any

Figure

in

is
phery

roller

adjustment.

of

of

roller

of

move
advantage

An

recently

H represents

to that of Figure

replaced

is

gear

takes

the

the bell crank lever.

is upward,

in Figures

the

reached

injury

represents

I

which the

fastened

of

which a small roller is made

is

the arrow

the

movement of

upward,

the heart

downward for 180" of the revolution.

entircly

come out.in which_ the necessary reduction

producing

F

provision

revolution

the limit of its

to the threads or

complete

an eccentric heart shaped

attached to the movable

When

as shown in the

and

passcs

thaL the fine adjustmcnt never

ncw fine

,FB

fine

a

adjustment enscmble

G except that

by a

worm-gear device. A

place

of the

The

no

and G.

On all of

is

made for

of

the shaft

another

gear

gear

the

heart shaped

the

worm-gear fine adjustment

circle is used. On

cut,

will continuc to

undcr thc roller whcn

atljustment

is attained by

gears

splrr

working in

It is very

just

described. It

dircct upward

Fis. J

made so

l4

that the

justment

All standard

positive

head is represented

impulse is

quite

the micrometer

and

nut

impulse from

lateral

thrust as is

the above described

automatically stop-

when the adjustment

excursion,

gears.

cam on the

segment

the long

the

also the

arm

short

thus avoiding

gear

this

peri-

to revolve. This

parts

of

levolves in the

one of

the

cam

so uritil

do

the fine

direction

components

forces

the apex

it

will

then

It has the

"runs

(see

Figure

means

similar

conjunction with a lever.

different

of a

to clock

from the

provides

thrust.

microscopes are now

The

always upward

out."

J) has

chain

gears

types

the

fine ad-

F.B.

at

the

of

slightly

against
allows
the

sing

front

the cover

uncertain
the cover

ff

a

movable

the

force of

when

the

one

down

of the objective should

glass.

observe the

glass

looking into the eyepiece no

compressed

parts

compression spring.

is not

Avoid

before looking

is noticed by turning

possible

possible

It is

that the

objective is resting on the

the fine adjustment may have " run

that

so apt to cause

this contact

proximity

the

spring. The mechanism

to

descend

come

if

of

into

gravity

by

Therefore

damage

into

contact with

possible.

objective to

the

eyepiece.

the

change

fine adjustment,

cover

in

If at all

of

it is

and

focus-

if

the

focus

quite

glass.

out." It is always bcst to kecp the finc adjustment

about midr,vay in its

provided

it

will be

near the midway

positivc

with

necessary to

point.

the fine adjustment

pin

loose
been misplaced. See

in the end of the

range. If

stops :rt
place

If the

head at

micrometer

page

12.

the microscope

ends of its cxcursion,

the

the rnechanism

microscope

the top

of

screw may have

the arm, the

is one

sornewhere,

is one with

The Coarse Adjustment

The Coarse Adjustment

tube is now affected
the diagonal

American and

the

rack and

ferent. Both are

except for the oil

way

The

bearings

on the
Do not strain the teeth

the bearings

are not clean.

surfaces scriously interferes.

are

llack

A little

very

the surface will clean

or rapid movement of

on all microscopes

pinion.

lluropean

good.

grooves

closely

of the rack and

and forth over one another when they

xylol or

them. Do not use emery o.

The bearing surfaces on

instruments

'Ihere

is no advantage

on Spencer microscopes.

fitted. Any foreign

pinion

chloroform rubbed on

by

are

the body

means

quite

either

matter

forcing

by

dif-

?;r"

of

the

abrasive.

other

them

oil

affin

that

screws

a

Do

or any

accumulate

or watch

oil

the

at

provision here

fill the

not

other

The body

support

obiectives

the

scoping-draw
length

ly and

down

the

contact with

for the

eyepieces

of the tube

easily.

the

objective by

When

slightly

will

tube

the back

teeth

foreign

these

in

tube,

principal optics

are located

at the

tube

In

whole

the

a

with

If the bearings

oil).

stay in

not

of the

taking

for

of the

substance.

teeth, clean

Body

The

together

at the lower
upper

provides

(See page

pushing it in be careful

tube to

body

bringing

cover

Binocular

A

comparatively

bv

single

a­interchangeable

the

device-

lifted oui

least danger

objectives.

both

whiih

obicctive.

objecfives.

by which

of

new bod.y tube

eyes may be

'I'hesc

with the

'lhis

particularly

is

either body

place

and the

of disturbing

Asillustratedonnextpage

cemented

two

is divided

16

by

bearings

good

pinion

are

free lubricant

acid

placc, tighten the little

box.

up lost

with.

rack

If

them out.

Tube

with the

of the

end of the

The

end.

means

a

?

. It should

)

injure

the objective

glass.

Tube

Body

has been

used while

binocular

single tube

true

when loosened

other replaced

the focus of the

the light

prisms

immediately

perfectly

become

makers have

All

motion and

paper,

anything

tube,

draw

microscope'

tube and

graduated tele-

for varying

move

not to

the.specimen

violently

introduced

working

body tubes

without

disturbing

of the

without

highest

from the

objective

clean,

(par-

so loose

wear.

paraffin

should

is the

Thg

the

smooth-

push

or

into

with

are

Spenc-er

be

may

the

power

above

tr'is.

pupillary

also

between

There

the
with the

distances.

variable

the two

two distinct

are

one with

tubes

The argument

more

are

they

are at
tance."Over
using thc

blending thc

done

it after

do

In looking

trouble.

rvhcn

rcst

against

parn.llcl tubes many

two

ordinary

in

some

into the

Normally when

K

to length

as

of

eyes

parallel

the

slightly

for the

rcstful for

looking at an

this is tlie

imagcs

vision.

practise.

converging

the objective. The 45o

surface
prisms

to reflect

to one

of one of these

is semi-platinized

half

side,

the other

through to be reflected
in

opposite direction

the

another

by

surface.

of light are again

ed upward,

eyepiece, by

cated directly belorv the

eyepieces and

rvith
arc rnovablc to and from

one another to accom-

modate

of the eyepiece tubes

One

to adjust

same

the

of these binocular bodies:

types

eyepiece tubes and the

converging

parallel

the eyes because

into

one

Quite

Some

looking

These

thern.

different

for

person.

toward the

seems

tubes

object

stubborn

people

a

tubes

at infinite dis-

have difficulty

picture

number are able

never accomplish

there

near

at a

the light

and allow

half

45o

each

pass

to

reflecting

tlvo beams

reflect-

its

to

prisms

lo-

rnoving

'I'he

eyepieces

inter-

a difierence

other

objective.

be that

to

"

the eyes

fact that when

is

as

regularly

is no sttch

objcct the

is

to

it'

l!1es o!
When looking

!ry

No adjustment
into

no
microscope

The

it

strain on one

for long

presents

the

scopic;

Be

satisfactory,

tinued work.

structure

entiated.

The
the fact

brilliant

therefore,

brighter field

require

Without doulrt

different antl
pretation.

light

converge from

at

of

slide

a

Lhe microscope.

readjustment

on

is necessary

image

binocular

permits

single

that

the use of

eye when

continuous observation.

picture

a

tube.

others

assert that it is not

as it may,

and more restful

Without

of

the object are much more

disadvantage of

that the divirle<l

a field with

considcr thc

is dcrnaudcd

the most cirilical

thc two views of

both rnake for a more intelligent

'l'lren'fort.,

both tubes cverr

less

cumbersomc.

Combination

To

overcome

recently

l8

this the Spencer Lens

designed a combination body tube

microscope,

a

the stage,

The images

is necessary

pick

to

body is

the eyes

when

in looking

up a

great

a

or

pencil

both eyes,

using the single

of the object

Some claim that the vision

the eyes

to the object.

observing

are converging.

immediately

appear as one.

away from

to make notes.

advantage

greatly

At

not

relieving

tube, especially

the same

obtainable

truly stereoscopic.

all agree that

doubt different layers in

using the

view

the

is much mbre

to the eyes for

easily

two eyepieces

lig'ht will not

sarne

thc

singlc

rnosl

though the

light source.

eyepiece

and when

definition

same

the

workers are

interchange

better

the exigencies

and resolution.

willing to use

Body Tube

Company has

plac-

the

Iooking

Again

because

time

with

is stereo-

long

con-

differ-

present

Many,

when a

object are

inter-

is more

providing

the

the

the

so

or

quick

a

and double eyepieces. For the

eyepieces are
eyepiece is

to bring the axis of one

side

of the objective, duplicating

that

single tube.

are automatically

easy interchangeability

and

used in

desired

All

the usual way. lVhere

the

body is moved slightly

of the

prisms

moved

between

binocular vision

the
the

eyepiece

coincident

the

conditions of

and the other eyepiece

out of

the way. The con-

single

both

single

to

with

one

the

it

is

venience

research

parts

when botlr

the'same

eyepiece

.i

I,'iu. L

of tlrrr rkrvice

workcr.

parts

is in worliirrg

lligrrrc

cycpic(:es

in tlrc

imrnediately appeals to

L shorvs

{rre used.

lrosition

position.

i

Fis.M

position

the

Figure

assumed when

M

buL

th<:

of thc

shorvs

ont:

The Nosepiece

The

so made that the nosepiece

provide

to

body

tubes of

the

objective being brought closs

The

convenience

has

become a

all microscopes are made

i. e., they are of

all the

others on the

a slight turn

brought

centered

of one will be

others. Thus a low

a

These

ctrely screwed into its

which
or if objectives

desirable

into

so

that an

finder for the

conditions

place

is

conditions

is individually fittcd by

place

in the

the standarcl

parfocalization.

and eyepiece.

The stagcs of all

layer of hard

a

permanently

ordinarily used. Should

balsam, immersion

not remove,

90

practically

is

proper

necessity.

tube length

of the

such length

nosepiece

a

quick

interchange of

The objectives sent out vrith

par.fctcal

that

of the fine adjustment

optical axis.

the

object in the center

close to the

higher

obtain

marked for it. If they are changed

from anothcr

center

power

arc likcly to

objective may

powers.

prouiding

particular

rnicroscope are

thc maker

noselliccc.

or a change

A change of tube

of eyepiece will affect

Ile sure to use the

Ihe

Stage

rnicroscopes

rubber

affected by

it

can

or composition which

the

stage become

the

or

oil,

anything

be cleaned

microscopes

all

necessary concomitant

and

enough to the

on

when

will be in

are

permit

to

stage.

objectives

the nosepiece:

one is in focus

focus within

when they

The objectives

are also

of the

of all the

of the

field

be used

each

place

on the nosepiece,

bc lost.

to

objectiue

Ilach objective

its

is se'

about,

used these

particular

length from

proper

tube length

are now covered

is

reagents, stains,

soiled

which

with a

water

little

xylol or

now

the

are

field

as

the

with

not

etc.,

with

will

chloroform.

gray

rub on a little

If this

black. If the

remain for a time; always wiping

oil

microscope.

the

All stages are

gular

work

circular
revolve

make

axis. Many

mechanical stages

used in the

are

because

stages on the larger, the research

around the

center

this

of

instrument:-on

stage, or as a detachable unit.

the

has

a tendency to turn the stage

gray

either rectangular or circular. The rectan-

color

is

great proportion

of their less cost and

optical axis. The

heavy oil

of revolution coincide with

the bctter

circular

rnicroscopes

either

stages

as

restore

to

of long

:ln

integral

whcre they

the original

standing,

ofi

before using

of laboratory

simplicity.

microscopes,

centering

the

equipped

are

part

revolve with

'I'he same

tions should be observed lvith reference to

of

has

reading of the

bearing

the

been advised

will locate an

easily

been

With the best

scopes

of thc

immersed

the

Spencer nri<:rosc<llrcs

the

fluid

when it is

even though the mechanical stage

removed from the

the

microscope stage so

stagc

slide

is hckl tlown so that a thickened

betwccn

objective carr not ciruse the
mechanical

surfaces, racks

for other similar

verniers on

object so that it can be found

microscope in

mechanical stages on the better micro-

slide is held slightly

the oil is not smeared

when the slide is

focrrsscrl upward. The movements

stagcs slrould be

.tlrc

is

also another feature by which

cover

any

above

that when

moved

glass

slide to follow the objective

even, free

pinions,

and

parts.

good

mechanical

the

the upper surface

the condenser is

the surface

over

about. On

and the

and

front of thc

no lost'motion.

let the

The

screws

optical

with

of

the

precau-

the care

etc.,

A careful

stage

again

may have

meantime.

the

better

immersion

of all

easy with

sr

as

of

The

Substage

The optics of the substage are the necessary comple-

ment

realized and the accurate

little appreciated.

capable of rigidly holding the axis

parallel

train

for

accurately centering the condenser

instruments.

centered
smooth

microscopes

best

on the substage.

There are

1. A

of

the stage holds the condenser

position.

It is

2. The

and for ordinary

The

optics above.

to the

Mechanically

and coincident

to

the

above

and

simple substage

not

condenser is raiscd and lowered

stage. Centering

Sometimes the condensers

by the

quick

maker. All the

delicate

are

three types

Rarely is

very satisfactory and

screw

acting scxtuplc screw.

and fairly

dclicatc. C:rrc

that the condcnscr mounting

substage

gummed

xylol or chlorol'orrn.

good

a

until

should

the threads if they do

starting

22

ring. If thc threads

or st,itftv "

oil and work the substage

it works frcely and smoothly.

run ontirely out of the

be

them in a

Their importance is

manipulation of the same too

the

the

with

screws

movements

as any

there

on

provided

of

Substages:

ring fastened to

any means

microscope.

the

with a

permanently in one

not much

substagc is vcry

is rcasonably

worl<

'I'he

movement

should be

is squarely

of

"

cut

When clean

not

place.

new

the

the refuse

start back

Remember

substage

of the condenser

of the

axis

furnish a

on all the

permanently

are

fine adjustment

the underside

for

focussing.

used.

generally

satisfactory.

by a

is smooth

taken to

screw

with a

relubricate

and down

up

the threads

If

nut do

easily.

little

too

must

optical

means

must be

All the

used

quick

see

in the

become

little

with

force

not

Try

are

there

best

be

as

six threads each

in the

become

and

nut.

rusted

oil them

the diaphragm several

oil over

the
bent or misplaced,

skilled

a

3.

The rack and

ideal equipment. By

workman.

definitely and

movable

pulated.

is

it

for

On

all the

are held

from
and out of

parts

When usirrg the best correr:ted

essential. A fine

the best

older

friction in

by

below. Usually

the

working best

If the leaves of

gummed,

or

thoroughly

the leaves.

times to evenly

Should the

submit

pinion

substage

it the optical

accurately

more freely

results.

forms the condenser

adjustment is also necessary

substage

the

ring swings

this

optical

axis carrying

with it. In manv instances

denser is.fastened to another

on

the other side. Whereas

used for many

as

are not

condenscr

hold

coincident
Again

impossible

touches

The

more

the

modcrn

usually

and iris

the r:onrlcnscr

willr tlrc

with thc

to

lrrirrg tlrr: iris

the largc

Spencer

that on them the condt'nscr

.lvith

vears

satisfaction,

equipment.

sufliciently

definitely back into

theire so

axis of the optical

irlro.r'c

Micros<:o;x's

t:onstruction it

k:rrs of

to a

the condenser-as

are

rigid

rvith

in its

the

clean

iris diaphragms

them with

by opening

them

held in

and

the iris
this

leaves become

to the

represents

parts

place,

definitely mani-

and its mounting

ring,

beneath the

arm

which

mechansim

it is not

The swinging

to

always bring

its

that

is mechanically

position

unique and

the iris

own

thread

xylol,

and closing

distribute

maker

the

are

more

and'the

condensers

put

being

to one

side

the condenser

swings

has

been

good

as

arms

the axis

optical

where it

train

in

the

axis is

above.

almost

it

should.

alone

proper

or

in

in

con-

out

the

and

in

position,

possible

plete

unit, which

fork shaped

or

top of the

on

is open

and when

optical

The lower

othcr

the

it.

upon

pletcly

of

any
adjustmcnt and

substage.

them as

provision

the

substage accessories

for oblique light, and any

unit slips

it resting on a

arm,

rigid

very

N Fis. O

Fis.

in front.

centered

train

parts

'l'he

frorn thc

part,s.

the

This unit

with.the centcring

of the rnicroscolle

supporl.ing

wholc

ring fits into the

arc built

cnscrrrble is easily removed com-

substage

'l'hcse fca,tures with

dclicate

If thcse bearings

previously

directed for

arm.

fine adjustment

The mirror is so mounted

movement of the

the

properly

not interfere with

24

adjusted

substage. When

the focussing

the direction

are mounted

in and out

horizontal

For

convenience

goes

definitely

perfect

is in

one on

up,

for cleaning

ever

become

similar bearings.

that it

the condenser

of
of the light.

other

in one com-

of

horse shoe,

a

bearing

the arm

place,

into

screws the whole

alignrlent.

fork and all

of the other,

top

or rearranging

the sturdy coarse

dirty,

mirror

ideal

clean

does

make the

is independent

the

General

PART

Theory of Microscope

II

oji,

Ray Paths-Axial Rays

IIICROSCOPB objective

A

forms an

/a

a \

con=idered

infinite

of

good

functions

first

'

image of the

the objective intersects thc object.

A

this

These rays would be brought to a

focus
the

eyepiece
lens

is

and the focal

of

number of

of these

two

idea of how thc objective

point

bundle

point

Ar'

at

objective,

did

places

in the

the eyepiece. The eye lens forms

an image of this

which can

which is completely relaxed. A small

rnovement

shift

of

is

will

so

that

the final image is not

at iniinitv.

obscrvtrr's

P

stanb strain

image

as'made up

points.

points

forrn tlris image. l'he

to

to

of rays

considcrcd is

be

point

'lvhere the axis of

proceeding

is shown in

in the

rrot intervene. The field

image

if the field

that,

will

Figure

lens of

may

A study

give

plane

this image at As

plane

the

plane

observed

be

of

the

whole

of

the diaphragm

of the eye lens

point

at

by

fine

adjustment

optical

infinity

an eye

system

formed

If such is the case the

put

eye

is

to make up for the lackFig.

under a con-

be

of an

a

bhe

from

P.

of

the

which

Fis. R

of

proper

of

Thls should be avoided.

always
instrument

To

of a

and

microscope.

blurred
gradually

is not

should

The

ered

the

examination

that

ceeding

therc

<:entral

bundlc

is,

that

cause

olr.iective

d.i'iation.

nrincinal

iet,trul

directed

the
tive

Doint
.,f thir bundle would

focus

to know

easy

properly focussed.

is

for this,

test

window

then

at a distant

look

If

at the

clears,

properly focussed

refocussed.

be

Paths-Field

Ray

the

from

no

is

ray

shown

special

proceeds

it

rav

ray"

at what

from

where

R,'

point

image

edge

of Figure

bundle

symmetrY

such

one

withoub
This

and

of

center

second

is

extreme

in the

however,

has

optical

and

instrument.

the

gaze

vacantlY

quickly into the

the

instant

first

instrument

the

to be

a

of

of the

of ravs

object

this

as existed

Figure

in

of this bundle

ray

significance

through

anY

rav is

is shown

the bundle.

maY be

of the

toward

there

t,he

all

cross

is not

It

the

that

out

object

image

and

and

Rays

consid-

Point

field. An

shows

R

Pro-

Point

about

in the

There

P.

be-

t}le

angular

the

ealled

the

as

It

called
objec-

the

oLherraYs

if

ib

at

not for the field lens

were

point

R1/ lies in the same

places

lens

field

of the

of the

crosses

is

called the

the

placed

rays of

it

made
is correctly

diaphragm and

eyepiece

the

point

to be

the

parallel

this image at Rg which is at the

deviates

axis at

Ramsden disc,

the

at which the

able to

bundle

it by the

to

focussed, and thereforc

of the eyepiece. The image

plane

in the same

the

point

exit

pupil

see the whole field.

surrounding the

eye lens, if the microscope

the

as

plane.

principal

,R D which

pupil,

or eyepoint. ft is

of the eye

form :rn image Rr'

point

The

so

ray

is

should

The other

principal

At'.

The

edge

eye

lens

that

variously

be

ray

are

it

of Rz at infinity.

Magnifi

easy to

is

It

farther

point

covers considerably

a

The magnification

of the distance

from

R1.

see

the axis

Thus the

Rr from the axis.

the

all our

magnification

object and

center

by the tube

objectives

of 160mm.

together

that the

on the distance

from

of the optical
determined
standardized the

is

objective from the

of the objective

of

tube length

it

the objectives

apertures.

cation-Objective

point

that the

imagc

of

microscope than is thc object

the

objective forms an image which

more area than does

of

Rr' from the axis to the distance of

of

objective alone is the ratio

the

A reference to the figure

R'/ is very much

the object.

will show

of the objective is dependent

of the optical center of the

also from the

of

distance

object

With

only.

is computed

objective from the

the

length. With

of

is

these

It is

with

image. The distance

the

optical center

the

determined by

data the

for a

engraved on the

their focii and numerical

objective

tube

the focus

magnification

standardizcd

image

length

of

boots

97

is

the

of

Magnifi

The eyepiece magnifies
jective

object ten feet away
certain

appears to

on the

size.

principle of

ff

twice the

be

it is the iarger

on the accommodation

can not easily focus

inches from the eye. If rve wish to see an

ten

on

scale

a

the eye it is necessary to

and the eye to assist the accommodation.
has a focus of
two inches from the eye and

at infinity.

the eye can not do, and allorvs thc

larger

other

In

cation-Eyep

the image formed

the

appears to an observer to

the distance be reduced to five feet it

'I'he

size.

it

appears.

But nature has

of

the

on

an

object

than it appears at ten inches from

place

a lens betu'een

inches the object can be

trvo

be

the

rvords

'lvith no effort at acconlnodltion.

only trvo int:hes frorn tlrc cyc il,l)l)cars to be five times

as large as tlr<-ngh

sible

disl-rlnr:e by

said to ha,vc :r, rnagrri{i<'rr,t,ion

il"

t,lrc rrna,i<lctl cyc. Thus the lens is

rvcrc

vir:rvcd

of

that our eycyriuts ilxr r:urrrpnted and

nification.

Magnifi

The

total

product

the

eyepiece. Thus if an

eyepiece is used the total magnification is

by multiplying

alone,

by

8A

I

cation-Compound

magnificll"ion

<if

a compound microscope is

of thc magnification of the objective and

oil

immersion objective and

98,

the magnification of the objective

10, the

magnification

iece

by the ob-

simple

human eye such that it

seen as though

lens

five. It

of the

rnicroscope. An

be a

nearer to the observer

put

a limit

is

that

does the work that

eye

see

to

'I'lre

object being

at the

nearest

is on

marked for

closer

object

the object

If

this

placed

it

object

the

this basis

mag-

than

lens

were

pos-

Microscope

10x

980, found

eyepiece.

In

'objective,

point

is

approximated

aberration

ration is

that they

fact
do

near the

point

dimensions.

by a

dark.
When
are faint

center

by
is

disc

Iight that
to the

only
up the

and that

ing area and

Thus contrast

hazy and washcd

of

portion

termines the

Defi nition-Spherical

explaining

it

paths

the

was assumed

of

to form an image. This

only

when the correction

good.

is

perfect,

would

light

that

not cross

crossing

image

series

whole

This

correction is

the

is spreerd out into

}'urthermore,

of concentric rirrgs

If the correction

the rays of

cross

at a

is

a wave

at

exact

an

point

in

pattern

motion.

point,

such

this

is

good

and diminish in width so rapidly

out, that

most critical test. If, however,

the

poor

the rings

remains the

surrounding rings. Since

portion

image,

the lost

only one or

are

bright and

same

size, but

should be concentrated in this

of the whole

this means that

light

will be

tend to haze the image of nearby

in the image is destroyed and it

out. This

definition.

It is only a matter of contrast. The

of

conccntrated

light

quality

of the <lefinition.

Aberration

rays through

that the

is never strictly

a microscope

rays crossed

true

for spherical

for spherical

a

bundle are so

point

if it

were not

Due

to this fact

jostle

but

a way that the otherwise

a small disc of measurable

central disc is surrounded

of alternate

called a difiraction

these surrounding

directed

for the

each other

liglrt

pattern.

from

two of them

can

be

the correction

broad.

large

a

The

portion

disc

central

of

is

the central disc is

pattern

the

spread over

goes

that

image

the surround-

to make

will be faint

points.

appears

is the true interpretation

in

the central

disc

at a

and

aber-

they

and

rings

the

seen

the

lost

the

pro-

de-

ss

nition-Chromatic

Defi

general features

The

not

the

color

the

good

axis

if the

for

of light

vary with

tion is

along

concentration

with
ical aberration

contrast

quite

poor

ble

which

easily by a

as

correction

obtain

to

a

the limitations

usual type

axis and
approach to a

other colors.

the

correction.

denced

especially

aid of the

the

of lens

spherical aberration

The lack

small fringe of color around

by a

when

of

these

rings

for

will

colors.

correction

the

different

in the central

so-called chromatic variation of

is not corrected. ft is evident

determines

poor

correction for color as

for spherical aberration. It is not

perfect

correction

of manufacture

is

corrected

correction

Achromatic

obliquc light

ncwcst

for spherical

perfect

of

glasscs

Aberration

diffraction

color. If

occur

at different

Their

disc will also vary

the

definition can be lost

for

of optical

for two colors

for one color, and a

objectives have

color correction is evi-

is

uscd. It

the mineral fluorite

and

to correr:t for thrcc r:olors on the axis

the spherical abcrration

bination must

termed an apochrornatic
obtainable.

ble except

even then it

objectives are extensively

because of their

image that is extremely

an

crispness of
color.

30

,"*

of nct:cssity be

such a lens

With

undcr the

is faint and

more

detail and

for two colors. Such a com-

very complicated. It is

objective

most trying

used

perfect

faithfulness

and is the finest type

no

fringe is noticea-

color

of conditions and

narrow.

pleasing

The

for micro-photography

correction. It

color

to the eye in its

of reproduction

patterns

the

axial

size and

will

correc-

points

relative

spher-

that the

by a

possi-

color because of

glass.

The

on

the

close

aberration for

such

a dark object,

possible

is

and to correct

apochromatic

with

forms

Resolving

There is a conception

scope

mount

is another

magnification

that

importance.

requirement

either of these. This

pick

woven in

to be

good

enough

out and

consider a

it.

seen

it

thousand times, and that the definition

a

so that

on

however, it appears that at a thousand

the threads

more than an inch broad, and the

sufficiently wide to be

them

see these fine details in the

power.

It

'I

{

I

a

suppose we

tern

such a distance

distinguishable.
pattern

magnify

is

distinctly, but

consideration this
thought,
nification

appear to be
between

ability to

resolving

to

indication of a thread

resolving

definition,

completely to

This

nection
definition.

I'

'l\

of

I

ties

work

Resolving
quantity

A

ure

power.

and more than

give

illustration is

between

is

It

of

is

an

by

a thing

optical system and for the

far the most

Power-Oil

of the resolving

called

Power-What It Is

among some users of the micro-

definition

and

This

that is

is

recognize fine detail.

piece

Suppose that

from

the

slight magnification will allow the

A

clearly and

the

very much larger

a

strictly true,

not

is

resolving

more

of fine cloth having a

this cloth is

eye

that

easily. Now

pattern

may seem su{Iicient.

of

which the cloth

However, the image

structure due to insufficient

the optical system, having

Thus

a true

given

resolving

enough magnification, fails

interpretation of the object.

show that there is no con-

to

power

quite

important.

and magnification or

apart from

Immersion Objectives

numerical aperture is the mcts-

the

power

of a microscope objectivc.

are of

for

important than

power,

the

is seen clearly and

the

As

an

pattern

suppose

scale.

example

On

On further

is

woven

seen easily. The

object is

may show no

other

finest

microscope

para-

there

ability

pat-

held

is not

we

first

mag-

should

spaces

called

good

proper-

at

The numerical

where n is the

olject

the extreme

and the objective,

i! Figure

the numerical
study

of resolving

book to

lowest index

front- lens of

give

will be touched

Power

from

It is at once

resolving power,

!9 lake

limits

can not

aperture

betwe_en

an index

were

1.52

a_per'rrre

t\at

The use of

in

be_yond

be much

the object

of rcfraction

designed to havc

between

led to the

aperture

lowest index

ray of

P. This

aperture

the derivation

of refraction

the objective

on

the Standpoint

apparent

it is

a large

which it is

would

woukl

more

be .86 if

thc objcct:rnd

bc

dr:sign of

the oil irnmersion principle

highest numerical

1.52,

the index

if

a condenser

as the objective

between

Figure

*

S*

pug"

3+

aa

the condenser

Necessity

S shows

of

of

at least the
is

the

is

expressed

NA:

n sin

a

of

refraction

axial

is

under

and a

derived

It

between

the

expression

power.

that

necessary

angle. There

not

than 60o. For

and

the objective

of onc.

oil of

is

bundle and

that

from

is beyond

here.

enters

the heading

of

the Diffraction

in order

to

are, however,

advisable

the

lowest index

ff, howcvcr,

an indcx

Lhc obje<:tive,

.86.1.52,:l.30.This

the oil

aperture

the oil. This

used,

and if an

and the

immersion

otherwiie

is

same numerical

sl'ide.

of Immersing

top lens of

a

condenser

by

the equation

between

the angle

the axis,

is

arbitrarily

a mathematical

the scope

between

shown

called

of

The reason-why

the object

into th-e

of

atrd the

expression

" Resolving

Theory."*

secure

to

design

to

60"

were

of

go.

the numerical

the

is

a Liglt

the objective

practical

This

medium

air having

the objective

refraciion

numerical

the

theory

objectives.

multi$lies

obtainable

only

true, howevei,

aperture

oil

contact

Condenser

-is

and the front

the

this

the

angle

of

the

by

used

Iens of an oil immersion

glass

cover

traversing

condenser

between. The ray marked

the system

and the slide,

objective

with oil

r

and

of

cover

thal

ded in

the same

and the

seen

through

any

two

to

the

cover

Ienses

to

under consideration. Let

the axis be

Fis.

S

ao.

Then its numerical

NAe:nsinao:l'30

ray marked

The

without

slide. This ray is
condenser

a way

an oil

and

that it traverses

tact and front lens

rection in the upper
struck

angle to the axis as the ray

reflected by the upper surface
lens. The largest

to leave the upper

bY the equation

the upper surface of

q-q

is shown

contact

the lower

between

deviated by the upper surface

surface

the

of

objective

the

lens of the

the condenser

possible

surface of the condenser

angle to the axis for

sin

an

with

contact

between

the

objective

glass.

thc ob.ject

a medium

that

Lhc

deviation

curved

thc fact

same

irrdex

glass

the

traversing

the condenser

of the

slide,

cover

condenser. If

it

?-p,

and

v'ould

:

r/n.

the

slide

is

shown

front

and

assumed

and

the

lens

the

p--p

between

the

It

[is

is embed-

index

cover glass.

the

s.yslem

surfaces,

that

and

angle

aperture

having

as

the slide

ra.y

without

between

the oil

as

the slide,

the

of

this ray

is

ft is

goes

the

due

has

two

the system

and the

of

in

oil

to its

this

the

such

con-

ray

slide

glass,

parallel

at the same

would be totally

not

leave

the

the ray

is determinecl

di-

Thus

the

these

conditions

It is evident

an

oil

contact

Iost

by not

d-enser

the

The

formed

solving

the

are

of

blend

assurned

rated.

of

cover

Resolving

size

images

separated

either,

together

It has

the

central

34

and the

of

by

power.

they

that

largest

numerical

is

aperture

NAq:nsinao:n/n:1.0

that

a large

between

having

slide,

glass

and

Power-From

Diftaction

the

central

a microscope

If

the

of

two

by only

will not

and

u'hen

already

disc

does

pait

of

the object

an oil

even

contact

though it

the objectlve.

Theory

disc of the

objective

centers of

points

the

lying very

small

a

appear

appear as one

to be separated

centel of one

circurnfcrcncc

I.lrcv will

lx':rr

ol'

[,lrc ccntral

lrv rLrry

rrinecl

lcngth

,

illumination,

I

ical

aperture.

the numerical

,,

smaller

disc,
discs

and still

been pointed

not

va,rv with the coner.tionq

vary

possible

the

benefit

and

the objective

between ihe

is

retained

Standpoint

under

of

having

between

of

corr-

diffraction pattern

determines-its

re-

two discs representing

close

part

of

large spot.

.jrrst,

:r.s sclrirnlt.etl.

the

disc

of

bcgin

together]

diameter

but

will

It is

lics on the

thc other,

to ap-

l'he

size

disc formed

objective

only

of

the light

will

and consequently

can lie

be seen

out

with

is

by the

and

be

closer

that

deter-

used

its

numer-

greater

The

aperture

the

central

together

as sepa-

the

*'ave

for

the

two

size

the corrections

quality

which determine

then, the
on

i!

The

sion for numerical aperture again involves the

that

wide

by a

separation between them. The sum total

lies in a cone of larger angle than the

resolving

the definition.

reason why the

light is a wave motion. When the

angle cone

process

the

power

quantity

impinge

called diffraction into

nating cone. In other words the light
into a wider cone by the

an uneven distribution of

For an

objective

to

show

it must take in all of these

of these

more

it

depict

the object. This is simply anotherway

resolving

the

resolving

the

rays around

the

decreasing the fanning out

objective

the

jostling

the

expected

be

is changed when it enters a medium

refraction.
having

a wave length

length of

of 1.52. This

li\

ll

1,

l,

medium

increase

index

medium

traversing

groups

object

the

power

power

by

will be

will be

the

to take

is less for the shorter wave

by a little thought.

It is reduced in the

.000368mm. in a

between

the resolving

physical

is the

the

decreases the

it, thereby decreasing

of

the definition.

not depend in any way

does

Evidently

n enters into the

rays forming a

on an object, they

are

groups

of

these

original illumi-

is fanned

process

it takes

showing more of the detail

object

in more of it. It

of

object and

power

of

light
all of the

diffraction,

through

groups

this

detail in an

in this cone.

in, the more truly

greater.

increased

can be

of

the cone

The wave

ratio of the

.00056mm

medium having an

reason why a

of saying

is easy to

It

if

the

decreased,

and allowing

so happens

lengths, as would

length of light

of different

in air

the objective

objective.

of the

length of the

wave

the fanning

new cone.

jostling

index. Light

has a wave

high

expres-

fact

jostled

with

groups

out

with

but

object

'I'he

will

in

that

see that

of

thereby

that

index

index

index

will

The high

light

out-due

a

of

I

li

to difiraction

objective

an

diffra.ction

that

image

which

should
must lie

the

means that

objective,

light enters

serves to

also

such as

shortest distance

The

shown as separated

be

around the

of a

pattern.

includes

be remembered

unbroken

in an

to

objective.

the

explain why

ultra violet

the

with a condenser

by the

of light

condenser

the brightest

This is the

I\tumerical

expression 2,/NA,

for

used

this

becomes

part

value

Limit of Resolut'ion

Aperlure Witlnut

.10
.25
.50
.66
.85 .00066
.95

1.00 .00056

1.25 .00045

1.30 .00043

The above

objects

two
viewed'under

36

table

that can be

the

The

more

its

object

angle

objective

the

of

resolving

given

that this high index medium

chain between the object

prevent

the

The above line of reasoning

the use

increases the

between

microscope objective used

by a

properly

is

that

where

illuminating

2,/NA. The wave

spectrum is

of the

in the

used

condntsr:r

.0056

.00224

.00112 mm.
.00085 mm.

mrrt.
rnm.

mm.

.00059

mm.
mm.
mm. .000225
mm. .000215

gives

conditions

smallest distance

the

seen as

and therefore allows

i

to take in more

then

can

fine

power

fanning out

of short

two

2,

the object.

of

detail

the
greater.

is

before

wave lengths

resolving

objects that can

immersed,

is the wave

Without a

length

about .00056mm.

I''imit

With

table.

of Resolution

Condenser

following

.0028 mm.

.00112
.00056

.000425
.000330
.000295
.000280

separate

indicated.

objects when

should

It

of

this

form

object,

and

power.

given

is

length

mm.
mm.
mm.
mm.
mm.
mm.
mm.
mm.

betwecn

an

It

the

be

rrotcd that this distance

rltrrrscr

ir,

'l'lris

nilication

irrst.llnce,
scparation between

.(X)0f]

is used. This

r.ondenser when

of resolution is not dependcnt

limit

providing

no

amount

mm. unless an objective

tperture is used,

ernphasizes the necessity

high resolving

sufficient magnification

two

with a

is exactly

halved

power

magnification will

of

objects that are

of at least .95

condenser.

when it

is rtxluit't'rl.

on thc Irr:r.g-

is

separated by

<'ott-

of

rrsirrg

I'irr

uscd.

show

l,lrrr

numeri<:ill

Proper Magnification

It is not necessary

enough

rcsolvable by

will

to depict

show no more detail and will

to use a

clearly to

the objective.

magnification

the eye the finest <let,rril

greater

A

materially dccrt'asc

the illumination. It will also tend

of

object

an

increased

can be

by

studied will be decreased

increasing the

tain advisable maximum.

focus

both decrease

The rnagnification should, therefore,

sible. The maximum useful

puted

by dividing .3mm.

contrast of the image,

of the objective
for

:rnd

magnification
t':rtcs

'l'his

t:vcr

work the

Assrrming
lnagnifi<,a.tion,

objective having a numerical aperture of

an

limit of resolution of .000215, the

a

a 15r eyepiece with a 1.8 mm. focus

represents

be used except in very unusual cases.

proper

used,

that

the highest magnification

magnification is much less.

the samc

thc illrrrrrirrrr.l.ion

so that the ease with

magnification above :r crt'r-

The field and the depth

vrith an increase of

magnification can

the

by

given

in the

should

Depth

qu:rlit.y of

used is 1400. This

be

of Focus

correction and

varies as the squart'nof

greatcr

magnifica.liorr

to decreasc

rather tltirn

magnificatiorr.

low as

as

be

of

limit

above table.

resoluliorr

greatest

object.ivt'.

that

I'or ntosl,

thc sn,rrrc

wlriclr

be

'I'hus

shorrkl

thir.n

l,lrc

ol'

pos-

conl-

l.ll0

t,otirl

irrrli-

numerical

the

aperture.

tration varies inversely as

numerical

the

quadrupled
glven

numerical aperture

of focus

aperture

the

and

can not be altered

definition. Strictly

increase in

depth

the indefiniteness

numerical aperture

of focus except to

greater

for

be
list lenses

apertures.

depth. If depth

work under consideration,

the

sacrificed

to obtain

having the same

is doubled

depth

speaking this does

of focus but

of focus.

should

the detriment

it.

Vorking

Working

cover

distance

glass

It decrcascs

apcrture

ical

focal rlist.:r,ttr:t:,

same

will havc

distance

lens. If thc

beyond

thereby.

also

its surfacc

:rnd the

gencrlrlly

thc

lt:ns lrts

is the free distance bctwecn

objct:tivc when

wit,lr

of tlrt:

objct:t,ivc.

tltc

slrortcr worhing distance.

<lcpr:n<ls

on the mounting

:r

lrrorninent

the working distance

The depth

the

of focus is

and magnification

except by

of focus

numerical aperture.

illumination

the

halved.

destroying

not

rather in an

Lenses

never be compared

of focus

is for this

It

focus but different

Distance

int:rt:rlsirtg

ottt: with the

having

of

the

is

a

resolving

thc ltttcr

powt:r

Of'

two

one having

valuable

power should

reason

lenscs rvith the

higher N.

The

mounting

pene-

or

If

For any

depth

the

the

result in an

increase

the same

for depth

numerical

is focussed.

:rnd numer-

of the front

projecting

is lessened

in

the

asset

that we

the

A.

working

PART III

Use of the Microscope

is

The

Equipment

MICROSCOPE equipment

A

rate, and some rvork requires

/{

ever-v rnicroscope

^

^

virlcd

with at least tw-o objectives,

<x:ulars.

is

1") :rre

irn<l

rrrrivcrsally

lrrrrn. (1-0").

rlcsired

<:orpuscles

rvorking

of

rrrrd
sir:rble.

lf

lrigh

irnmersion

is most

<'rrllcd

irr

rrrc of
rrt:L[.ic.
orrt:

ol'

rrtss.

llrrrl. is corrccl.crl

ol'

If but one ocular is

lrest.

two are

If

preferable.

pathological

used objectives

provided,

For ordinary

work the most

In some

a 3mm.

distance for working through the thick cover

the blood

other low

bacteriological

resolving

used. For

into

this rvork

trvo

Of the

nrost

cornrnonly supplied.

good

vcr.y

'l'lrc

lrcst worl<

olr.jccl.ivr:.

llrr'

(1-8")

a narrow

counter

power

or special

power

objective

use. The

great

is indispensable. The l.Smm.

extreme work the

demands the use of a condenser.

classes,

latter class the Abbe

worl< lrnd is

r':rn only

l.o :r.

'l'lrr.

to be

cases where a higher

is used. For counting blood

angled

is

used. For entomological work

work a

is required, is

high

the achromatic and

commendable

lrt.rlirrtion

;rclrrourlrtic

may

be

such an

e{ficient should

and

preferably

bought the

6X

the

are

4mm.

40mm.

and

biological,

desirable

l6mm.

the

(1-6")

(|ty',")

cytological

to be done,

1.5mm.

resolving

This condenser

be done with a

power

condenser

that approaches

condensers

very elabo-

outfit,

but

pro-

be

two

10X or l"

(2"

10X

histological

and

(2-3")

and.

most

and

power

with a

long

is very de-

work, where

an

(l-f

2)

(1-16)

required

These

non-achro-

is the

is

capable

for its cheap-

condenser

t,lrat

that i.rrc

is

is

also aplanatic

short focus

a

small in diameter.

For the

should be used.

achromatic

need not be repeated

and
chromatic
aperture

also

recommends

In

choosing

position

able

have room

and

sories and

to the using
in using

working

stage is

often used

one's self to usc thc

perpendicular

in that

Make it il

possible,
practise

to this and

reasonable amorrnt

injure the

are in this

lvhich

most critical

The

objectives has already been

objectives

than the

corresponding achromatic

their use for critical work.

place

a

where

he

for his microscope

reagents.

of the inclination

it if it is

with

ncccssary. Ikrr:tust:

more

fresh

in thc laborirtoly, it is llcst

position

position.

nrlc to

citlrcr eye interchangeably. A very little

lrse

cnablc one to do so. By

will

proper

'I'he

eyes.

this difficulty.

The best light is

some

authorities

40

obtained from

claim that the light from the

class. The best

means that they are

work

apochromatic

superiority

of these

of these

unusually

objectives

over the

pointed

here. The fact that the

generally

have a higher

numerical
objectives

Position

to work one

can

'I'here

comfortnble to

rnounts

should select

obtain

the best

is some controversy

joint.

light available

necessary a,cces-

and

There is no harm

do so. ff one

or fluirls, l.fre

prt:plrr:rl,ioIts

su<'lr

a comfort-

in regard

lrorizonta,l

for otrc to train

nricrosr:opc lvith thc tube in the

it

and rnakc

work rvith both

lighting there

of

work rvith the

new binocular microscope

rule to keep

a

eyes open, and,

paying

is no

microscope should

attention

reason why any

obviates

Light

white clouds, although

have

apo-

are

out

so

blue

sli1.

is best. Avoid

is so situated

Lo rnodify

is

frcc

is surne

lfor long

liglrt

<'onstant

light

trvecn

\Ydsbach

rlt'scent

vcry

I o

rrse a bull's

lt, is

lrct,rveen

<'r's

rnake

is

it

srrlphate

tl<'nser

:rs

to exclude

r'.!'t:

rrrirrroscope,

is

often

'l'lrc

if

sl.rongly

tlrc rnicroscope.

s('r'ccn

r'orrstructed

rvorl<er.

cirn

bc obtained

Al'l,r'r

ocrrl:rr

the light. If

from cross

distance from swaying

continued work on

one

has

in

is

tungsten

a

it and

burner or a small

lamp is

successfully.

also best, wherever

the

a

solution serve

and the biue

shade, or some

desirable.

lamps

recommended

that

With

stxring

rr.nr irr

the use of

that

advantage over

quality

sun shines

the

possible,

bars, wire nettings,

and

burner rvith

the microscope.

good.

Ordinary

fn using

eye

condenser

light

source

glass globe

glass.

all other

excepting

designed for

They

gives

that no stray

their

and maintained

that

plil<r', prr[.

light from the microscope.

shade

that

for

are

an ideal tone to

use

Focussing

olljective

ur

sunlight.

direct

in,

select

branches

If the room

use white shades

a rvindow

etc.,

and which

of trees.

any one subject

daylight in

intensity.

"

The

Daylight "

that

best

glass

A fair substitute

arc lamp. A

artificial lieht

between

possible,

and the specimen.

filled

with

purpose

the

It is so mounted

cutting ofi

which

microscope illumination

long continued

provided

light reaches

ideal

illumination

:r

l.ransparent or semi-trans-

whitened incan-

daylight can be

it is

it

and

to use

ammonium

strikes

with a

the light and

for

any length of

(low

the mirror.

a blue

Some work-

of

both the

light

all

the mirror,

"

Daylight "

the eye of

power)

in

from the

work with

conditions

which

artificial

it is

artificial

be-

is

used

best

glass

copper

con-

shade

a

An

are

so

are

the

time.

and

an

a

parent specimen

the

io

-"diutt

and adjust

may

as

Focus
adiustment

glass,

at

adjustment

Be carbful

ing it.

and

When

means

ment
Do not

with

the

being

the

Ihis

the

the

of

to

expect

even

is

It

the

ment, becautc

on the cover

adjustmcnt
men about

necessary

the obj<x:t.

keep
the'specimen

movbmcnl-

the

point

where

is

bbject

focus.

be

It will

reverses

scope

to ilrove

is moved.

42

line,

so as

it

judged

be

body

until

careful

eyepiece,

until

to

not

likely

is

specimen

object

coarse

the-

obtain

too

more

adjustment

fine

,ttty

<,ui

is a

olrst:rvtr

to

<:otrt,ittttillly

to

wltt,'r

thcrc

apt

morc

noticed

the

the

in

This,

on the

take

illuminate

to

looking

by

down

tube

objective

the

not io

up

focus

specimen

the

pass

by

to occur

and

thin
is brought

adjustment,

sharpest

the

great

a

dangerous

irrtp:tt'b

ttot lrt'

tntxlcrn

ottc

l'txrtrs.

itt

l"rying-to

rnly

no

is

rliff<rrt:rrt

object,

to be

during

irnage,

direction

with

along

stage,

hold

swing

of the

directly

by

nearly

it'

touch

carefull;'

cornes

focal

this

if the

transparent.

fairly

focus

in tbe

range

focus down

to

with

than

of tlrc

clsilv, ttnlcss

f,'lt

Whilc

onc.

parts

the fine adjustment

worl<.

It is always

get

be trying

-and,

noticed

this

and

as

movement

that

opposite

fact that

the

the-rnirror bar

edge of the

object as

the

means

point

light be

use the

to bring

at

of the coarse

touches.

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with

plainly

without

into

well

fine

to

it'

the

rvith

the coarse

into

too

focus by

fine

out details.

adjustment'

any

the cotrse-:rdju.st-

olljcct-ive

of tlrc

frorrt

of it,

the

it will

tnoving

well

a focus,

for without

to focus

-again,

the

the

to that

the

comes into

lens

that the

specimen-seems

in which

the microscope

mirror

evenly

cover

the eye

view.

notic-

intense

adjust-

extent

the fine

speci-

be

to

to move

upon

moving

micro-

rrrl,gnifies

perplexing

spcr:irnen

pnrctise

orrc

'l'lrc

rrnrl oculars

r.vor*ing

'l'lrcy

llrrrs

After

<.rrn be used

plrrt.

orr

il nosepiece,

sirnply turning

rrrrrl

sirrg

rrrrrl

il'

l.his spot

il

rvill

ll,

is

rrr:ulc

ol'

l.he

a

rrifir:ation

:rrc

considered.

o

l

Lhe rrosepiece,

llrr:

r':rrrt,iou

piccc.

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olr.itxrtivcs

it

sclcrving

:r s lrclirrrr-

the movement

at first,

just

comes

put

to

the

beginner should ah'r'ays

first. The

distances

always show

give

one

obtaining

to bring out

If

the objectives

and makes

where it is

the delicacy of

specimen

low

and are not

a larger

a better idea

general

this

greater

are

the change of

one objective

the other

(except

a.gain

be

too much to

absolutely

into it

for

a slight

hunting

is in the

somewhere

centering can

up the

center of the

ask of the

parfocal

without

in

the field

be appreciated

and the extremely

When

the objectives

re-focussing

objcct

to always

\Vhen rro

of

are

thc

necessary.

focus

revolving

lncuns

the

othcr iuto

as rvell

it

wanted,

movement

where

iust

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the

porver

objectives

so

portion

of

idea

detail

parfocalized

objectives

out

the

necessity

turn of

and

In

up

nosepiece

unscrewing

the

particular

field

of

maker

centered.

small

and

doing

before

place

its

as

the

difficult

and

no

farther.

which

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wants.

lowpower

apt

to

of

the specimen

general

the

the

higher

in

any

and

of

the

fine

spot

of

the

the

higher power.

that

the

The

when

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not

again

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turning

is

used,

of

one

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specimen,

to

move

the

With

enables

objectives

have

ionger

be

injured.

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contour.

powers

particular

centered

is

made

by

optical

of

adjustment)

desired,

axis

re-focus-

for

low power

lenses

be

delicacy

the mag-

examineri

thus

fitted

hunting

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up

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ile

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44

ntirror.

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ptop"t

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power

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We

matter

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seen

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rro

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If

artificial light

tlrat

'l'he

lf

l bull's eye

the light source

tlrc light source

k'rrs

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llris

lr"rrrn

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mirror

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done.

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than

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axis of

Other considerations

central

trees,

mirror.

to clear the mirror

itself should

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the image of

more

is used, the mirror should

nearly this image

condenser is at hand, so

and the object

will

of

objective.

the

above rules

theeyepiece

necessary

be

light, by use of the

placed

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even

with the top

is used, the size of

should

may

F-or some

quite

be

rule

by trial."* The

a focus like a lens.

bc found that, in focussing

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rn:ry

if tlrt: instrument is

llrt

Microsrrrlrr'-(lirgt:

so

be

the cone

light.

of light,

to its

In

working

axis. This can

window sash,

If the whole microscope

turned that

be turned

upon it.

the light is seen in

covers the mirror the

seen in

be

are followed it

that

the

to vary

the width

the better microscopes, as nearly

surface

of these reflections

so that, if

that a

the center of the back

will be found upon

fieldisevenly

of the stage."When

the

the rays of

reflected
are more impor-

from it

not

with daylight,

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not

can

possible,

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the center

place

sharp

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diaphragm, which

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image of

illuminated.

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objects and some objectives

widely departed from; one must

concave

mirror

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from right

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bc due to an imperfection in the

good

in

repair,

45

to

from

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This

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position

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centered.

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the

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of light

The

nlane

denser

,rri".or"op".

46

one of the

any

than likely

though

is even

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means

more

Manufacturers

mistaken

axial

shifting

reputable

that

the mirror

apparent

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Oblique

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noticed.

light

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upon

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lrt:n<raLh

source

high

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amount

providing

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to

when

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microscopes

bo a

a condenser

powers

of

ils aperature.

should

the

makers,

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bar

may

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often condemned

are

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A slight

give

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swinging

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lateral

the

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each

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rnoLion

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of

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are better

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of the

as much

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used

quite near

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median

than

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intcrvening

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to remove

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{.o rctain

l,he mirror

.r'r'r
'l'o

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I

lhc

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ing

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If the

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the

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possible.

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the mirror

condenser

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of

such

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condenser.

whether.he

and

the

secure

the axis of

The

operator

gets

the images

the images

so

that

of

back

or

he

they

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the

objective

central illumination

the

condenser

axis of the objective.

so

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of the

can,

of

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focussed

the back of

can

the

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therefore,

diaphragm.

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just

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have

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accomplished.

the objective.

scre,ws

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free

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light

sky

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Lowering

destroys

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better

results

without

get

can

best

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center

be tested

When

of the

through

of

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In

the

thc factory

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the

will

also

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is

focussed

used

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or

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proper

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decide

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results

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should

microscopes

of

the

'Ihe

centeiing

by observing

the

diaphragm

Close

the

appear
The
of

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cheaper

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accomplish

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the

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on

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sharp

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the

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of

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;rll.r'rt:rl.

47

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than

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rt

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of the object.'I'his

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with the microscope

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ration

54

known

Color

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objectives are corrected for

The

media

kept

horizontal,

tation, and they will

seemingly

The fact that

magnifies it may be

and

Beside any movement

times a

particles

focus

With

one

to

fluid, always cover the drop with a

parallel surfaces.

with

currents

be seen with a

running up

the microscope

peculiar

from

indefinite to and

position

one

Brownian movement.

In studying

the tissue
about to bring
and by

different

view. Where

be studied

Sometimes
sam

appear

sections a

only

can

different

focussing

levels,

or

serial sections

in relation

sections which

cloudy

be

with the fine adjustment

optical

and

failure to thoroughly
putting

the realm

scope

the

into the balsam.

it

of laboratory

of

this little

The bright

become clearer

oblique light the bright spot

side. In studying water, blood

If

will be set up, due to

hill.

reverses every

mentioned again.

due to currents

while the edge

cover

passing

rays
such a mount

magnified velocity

movement

there is

glass.

through

is not

gravi-

some-

fro movement

to another.

This

called

is

true idea of the structure

obtained by

parts

planes,

are

moving the slide

into the.

successively into

each

used

optical axis,

to

bring

section must

to its neighbors.

freshly mounted in

are

indistinct. This is because of

dehydrate

the specimen before

But this brings

technique which

volume.

us into

is

bal-

beyond

MAGNIFICATION

il'hc rnagnifit:a,tion

o<lrlurs

ttttl

tti(icrr,lion

ot:rrltr.

of

of

The ma,gnificiltions

For instance:-the

(magnification

(6 x

aa) 26a.

of

rntv

t;lrc

bc

objcctivc

Focus

48

mm.

40 mm.

32

mm.

16

mm.

Itr

mm.

3 mm.

1.8

mm.

1.5 mm.

magnification

44)

when

of any

obtained

by the

<lf

<lll,i<rctivt:s

l.ht:

used

TABLE

combination

by

multiplying

magnification

ilrc as follows:

Magniticatilm

2.2

2.8

4.0

10.0

44.O

60.0

95.0

113.0

of the 4mm.

with the

of objectives

mag-

the

of

tlie

objective

6X

ocirlar

is

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Spnmcnn

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