34 BACTERIOLOGICAL APPARATUS 
‘“ Sometimes sections which are freshly mounted in balsam appear 
cloudy and indistinct. This is because of failure to thoroughly dehy- 
drate the specimen before putting it into the balsam. But this brings 
us into the realm of laboratory technique, which is beyond the scope of 
this volume.” 
TaBLE II 
SPENCER LENS COMPANY MAGNIFICATION TABLE 
Tube Length, 160 mm. Image Distance, 250 mm. 
Objec- Initial OLULARS Objecec- 
tives, Maegnifi- a as as as —— tives, 
mm. cation Ar 5 6x | Sx 10x | 192 | 15r | 20x | ™m 
48 22} 8] a2) i3/ is} 22] 27] 33] 44] 48 
AQ 28/| i| 14] 17] 22!) 28] 33 | 42 | 56} 40 
32 4 16 20 24 32 40 As | 60 SO 32 
30-22 2—4 5 4-9 | 5-12 | 8-19 |10-24 |15-35 |18-43 \20-48 30-70 |30-22 
25 4 6 24 30 36 48 60 72 90 120 | 25 4 
16 10 40 50 60 80 100 120 150 200 16 
12 15 60 75 90 120 150 180 225 300 12 
8 20 80 100 120 160 200 240 300 400 8 
5) 36 144 | 180) 216; 288 | 360; 482; 540) 720 5 
4 44 176 | 220; 264 | 352 | 440; 528 | 660; 880 4 
3 60 240 | 300; 360] 480; 600 | 720; 900) 1200 3 
1 950 | 1140 | 1425 | 1900 | 1 8 
1 109 436 | 545; 654] 872 ; 1090 | 1808 | 1635 | 2180 | 15 
Or 00 
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When using the camera lucida with the paper lying on the table 
add 60 per cent to the above magnifications. 
MIcROMETRY 
This has to do with the measurement of objects under the micro- 
scope. While there are several ways of doing this the micrometer 
eyepiece has the widest application. More accurate results are obtained 
because the real image is measured. Since this image has been magni- 
fied by the objective, the ‘‘ micrometer eyepiece ”’ must be standardized 
for each object. 
The Spencer Micrometer Eyepiece No. 425 is described as follows: 
“This micrometer eyepiece represents the highest type of pre- 
cision in construction and guarantees the greatest possible accuracy 
of measurement. Instead of the usual cross hairs, a finely ruled glass 
scale is used in its construction, each interval in the scale being exactly 
