MAGNIFICATION TABLES ae 
shreds in the vitreous humor of the eye which cannot be removed, but 
which can easily be disregarded. 
“In water mounts and fresh balsam mounts one is apt to find air 
bubbles. To be sure that the object is an air bubble, focus up with 
central light. The bright spot in the center will become clearer while 
the edge will become darker. With oblique light the bright spot 
will be thrown to one side. In studying water, blood or any fluid, 
always cover the drop with a cover glass. The objectives are cor- 
rected for rays passing through media with parallel surfaces. If such 
a mount is not kept horizontal, currents will be set up, due to gravita- 
tion, and they will be seen with a magnified velocity seemingly running 
up hill. 
“The fact that the microscope reverses every movement and magni- 
fies it may be mentioned again. 
“ Beside any movement due to currents there is sometimes a pecu- 
liar indefinite to and fro movement of particles from one position to 
another. This is called Brownian movement. 
“In studying sections a true idea of the structure of the tissue 
can only be obtained by moving the slide about to bring different 
parts into the optical axis and by focusing with the fine adjustment to 
bring different levels, or optical planes, successively into view Where 
serial sections are used each section must be studied in relation to its 
neighbors, 
TABLE I 
MAGNIFICATION TABLE , 
Bausch & Loms Oprticau Co., Rocusster, N. Y. 
Tube Length 160 mm. Image Distance 250 mm. 
Objec- EYErinces. Objec- | Working 
tives, |" tives, Distance, 
mm 5a 6 4x | 7 5x 10z 12.52 Inch mm. 
48 Q 10 13 15 20 25 2 53 
32.0 20 26 30 40 50 13 38 
16 0 50 64 75 100 125 2 7.0 
8 0 100 130 150 200 260 $ 1.6 
4 0 215 275 320 430 560 4 0.6 
4 Ox 215 275 320 430 560 4 0.3 
3 Os 285 365 420 570 740 $ 0.2 
1 90 475 610 720 950 1260 ts 0.15 
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