FOR THE ADVANCEMENT OF SCIENCE. 518 
was *'resolved " into three rows of “beads” or ** hemispheres," perfectly 
distinct and unmistakable, which occupied, of course, the position of the 
middle and edges of the spiral. They were illuminated by parallel light, 
very enoda under a 1-15 objective of 175° worked at a power of 3,000 
diameters 
Mr. E. Bicknell, of the Museum of Comparative Zoology at Cambridge, 
Mass., exhibited some diatoms recently thrown up by the sea at Marble- 
head, Mass. The deposit first found belonged to brackish water, as in- 
proof of the recent encroachments of the ocean upon the shore-line in tha 
vicinity. 
The Test Plate of Nobert, who has now “gone to the war,” and Dr. 
Woodward’s photographs of the same, were exhibited by Dr. Ward, 
chiefly in the interest of that part of the audience who were not profes- 
sional Agee eis and might be unfamiliar with these wonderful works 
an 
ists had seen the eden jio with powers of only five or six hundred 
diameters, In regard to the use of photography as a test of structure 
under high powers and difficult cireumstances, we may learn a lesson 
lines, which manifestly have nor da ta ce to the appearance of 
Scratches on glass as seen under suitable pow 
Dr. Ward had also been Gia te the idees of seeing two planes of 
the object at the same time with the Wenham's Binos ular. The eye -pieces 
conjugate foci below do not coincide. Some microscopists have attri- 
buted much of the stereoscopic effect to this fact, which, however, does 
ff 
difference of planes is most considerable), either to the stereoscopic ef- 
fect, or to the increased distinctness of definition above and below the 
plane of most perfect vision. 
An abundance of instruments were furnished by members to illustrate 
their discussions, or for the general work of the subsection. The first 
class stands were mos stly of the make of Powell and Leland, sus Beck, and 
Crouch, of London, of Nachét of Paris, and of Zentmeyer in this coun- 
try. The “Jackson” model of stand, with a curved arm, seems to be 
