78 THe MIcROSCcOPE. 
was as high as could be used by the objectives and fully illuminate the 
object and with these appliances the lines showed with great distinct- 
ness. 
We then used an homogeneous immersion—Zeiss 1-18 numerical 
aperture—1-28 with the following eye-pieces : Beck No 1, supra ampli- 
fication, 5; Beck No. 2, supra amplification, 8.33. Tolles 1 in. supra 
amplification, 10; Beck No. 3, supra amplification, 13.88 ; Tolles 4 inch 
supra amplification 20.83. The illumination was the same except that 
the angle of light was as oblique as the condenser could give. With 
all of these eye-pieces the beads showed very strongly. 
The slide mounted in a yellowish medium witb a refractive index 
said to be 2.3, did not seem to present any marked superiority over the 
other. 
Your committee would expect these media, particularly the color- 
less one, to be of great value if they keep well. Their advantage in 
the ‘study of diatoms is obvious. We would also expect them to be 
even more useful in histology if preparations can be transferred to 
them without injury. They may also be of great service in the study 
of bacteria. 
By the process of staining, now necessary in the study of these 
structures they are shrivelled and perhaps changed in other ways, and 
we may hope to learn much more about them than is now known if 
they can be studied in these media in a more natural condition, 
Respectfully submitted, 
B. W. THOMAS. 
LESTER CURTIS. 
H. A. JOHNSON. 
H. W. FULLER. 
H. J. DETMERS. 
HOW TO MOUNT CASTS. 
E. E. JACKSON. 
Hae is my method for preparing and mounting casts. It is 
simple and the result is good. If you think from specimens 
sent it is worthy publishing, do so. 
After allowing urine to settle, pour off and wash sediment 
repeatedly with clean water, the object being to get rid of the 
albumen. The white sediment consists of casts and epithelia. 
Have ready a solution of eosin 5 grs. to 1 oz. (water 3, alcohol 
1), pour it on sediment, allow to stand 30 minutes, then wash 
