674 
PROCEEDINGS OF THE SOCIETY. 
They also exhibited a new form of eye-piece named the “ Holoscopic,” 
which was fitted with an adjustment to render it either over or under- 
corrected, and suitable for use with both achromatic and apochromatic 
objectives (see p. 651). 
Dr. Dallinger was very glad to find the makers were beginning to 
realise in earnest that there was a want for something which was both 
good and cheap. He had seen this little instrument, and thought it 
would admirably answer the purpose for which it was intended ; and the 
coarse adjustment was so well made that he found it worked with ease in 
focussing a 1/8 in. objective. 
The President thought it was a good sign that they now had a Micro- 
scope of this kind with only a coarse adjustment in place of the sliding 
tube and fine adjustment ; an old one which he had in his possession for 
many years had certainly proved a very good tool in his hands. This 
Microscope was strongly made and well fitted, and would no doubt be 
found a very useful instrument. 
Dr. Measures exhibited a new Microscope for photomicrography by 
Zeiss, the chief features of which were a wide body-tube and a new form 
of fine adjustment, which admitted of the arm being of any length with- 
out throwing the weight upon the fine adjustment screw. The milled 
head was graduated to 0*002 mm.; an entire revolution raised or de- 
pressed the tube 0*04 mm.; and the screw was protected completely 
from any injury from overwinding. 
Dr. Dallinger said it was a matter of interest to find a firm like Zeiss 
attempting to reduce the speed of the fine adjustment. The way in 
which they had done this was most ingenious ; for though the thread was 
the same as before, the manner in which it was acted upon was entirely 
different. It was effected by means of an endless screw which acted on 
the micrometer screw ; # and as the milled head which worked the endless 
screw moved the micrometer screw only slightly by each revolution, an 
extremely slow motion was obtained, being only the 1/635 in. for every 
revolution of the milled head working the endless screw. They had 
always protested at the Eoyal Microscopical Society against the fine 
adjustment having to carry so much weight, and they were therefore very 
glad to find that this one only had to lift one-fifth of the weight usually 
put upon the fine adjustment of an ordinary Microscope, but this arose 
from the fact that the body was made of aluminium, not brass. 
The President said their thanks were due to Dr. Measures for show- 
ing this Microscope. The method adopted was certainly a novel way of 
slowing down the fine adjustment, and it was the first time he had seen 
an endless screw used to reduce the motion. The reduction of the 
weight upon the thread was also a very important improvement, and 
another good feature was the length of the arm. . He regarded these im- 
provements as a concession to the English idea, and an admission that 
some improvement was, after all, possible on the Continental model. 
The President said he had another Continental model to bring before 
them, — Keichert’s Austrian model, a new feature of which was that the 
