1882.] 
753 ) 
NOTES. 
Some years ago an improvement upon the old oxy-hydrogen 
microscope, by Mr. John Browning (“ Quarterly Journal of 
Science,” vol. vii., p. 285) was noticed in this journal. The 
“Journal of the Royal Microscopical Society” for Odtober 
(p. 673) contains an abstradf of a paper by Dr. Hugo Schroder 
on “ Projection Microscopes,” with a description of an instru- 
ment, constructed by himself, with which it is stated a power of 
from 100 to 2000 can be obtained, the source of illumination 
being an ordinary petroleum lamp : a figure of the instrument 
accompanies the abstract. The perfecting of such microscopes 
would be a desideratum, as at present the only known mode of 
exhibiting magnified objects on a screen to many spectators, in 
a manner at all satisfactory, is by the enlargement of photographs 
by means of a good lantern. It is to be hoped that English and 
foreign opticians may be able to effect further improvements. 
The same journal (p. 726) quotes Prof. C. H. Raid (“ Amer. 
Monthly Micro. Journ.,” iii. , 1882, pp. 71-2) on the advantages 
offered by the recent improvements in dry-plate photography to 
the microscopist. Of dry plates it states : — 
“ 1. They can be kept for any length of time, and used as 
occasion requires. 
“ 2. If not convenient to develope the plate at the time the 
exposure is made, it can be put away and developed at 
leisure, even after an interval of weeks. 
“ 3. No dangerously poisonous chemicals are necessary in the 
developing process. 
“ 4. They are so sensitive that the light of an ordinary kerosine 
lamp is amply sufficient to photograph objedts with all 
powers not higher than f-inch objectives. Probably a 
4-inch objective could be used by properly arranging a 
system of condensers.” 
At a meeting of the Camden (U.S.A.) Microscopical Society 
Mr. J. Carbutt took a negative from a spider’s foot with a 2-inch 
objective and an exposure of 2 minutes, and from a sheep-tick 
with an exposure of if minutes, the shorter exposure being due 
to the objecft being much less dense and yellow. 
The Netherlands Scientific Society of Haerlem offers prizes 
for essays on the structure of the kidneys of the Mammalia, on 
the peripheric nervous system of the various osseous fishes, and 
