338 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
forceps lias a trifurcate lower fang between which the slip is inserted. 
The two upper teeth of the fang are grooved, and are set at a right angle, 
so that a square cover fits in accurately., and is held firmly by the upper 
fang. 
(4) Photomicrography. 
Photomicrography. ' — Mr. T. J. Bray considers the practical employ- 
ment of ordinary objectives in photomicrography; he shows that for 
ordinary work it is not really necessary to have specially corrected 
lenses, and that with ordinary objectives of low power good results can 
be obtained. The objective he finds most useful is Bausch and Bomb’s 
student’s 3 in. to 6 in. variable ; this with a long bellows camera gives a 
wide range of amplification, which may be further increased by the usual 
methods of photographic enlargement of the negative. For large nega- 
tives a dark room takes the place of the camera, the Microscope and light 
being arranged outside. With the long bellows camera, the focusing 
arrangement of Dr. Mercer is adopted. This consists of a wire from the 
back of the camera, which is connected by a vertical lever to a horizontal 
extension of the pinion shaft of the Microscope coarse-adjustment. The 
picture is focused, with the aid of a 2 in. eyc-pieco, on thin cover-glasses 
cemented on the ground-glass screen of the camera, as is done by Walms- 
ley. Many details can only be brought out by using a colour screen ; 
this is a bichromate cell, as is used in cloud photography. Photographic 
details are given in the paper. 
Acetylene Gas in Photomicrography, j — Mr. W. H. Walmsley has 
previously suggested the use of acetylene gas as an illuminant in photo- 
micrography/! The light which it gives is white, very brilliant, and 
absolutely steady ; there is little heating and no smell ; it is portable, 
simple, cheap, and safe, and is always ready for use. All these advan- 
tages are not combined in sun, lime, magnesium, electric, or other lights. 
The flame, which consumes one-tenth to one cubic foot of gas per hour, 
is enclosed in a metal case with a glass front ; the flat flame is placed end 
on, or pencil flames are placed behind each other with diaphragms 
between. The author, for his own use, renders the light monochromatic 
by means of a cobalt blue cell placed in the substage of the Microscope. 
The use of an acetylene flame as a standard unit of light is suggested. 
An automatic machine for generating the gas from calcium carbide is 
supplied by Walmsley, Fuller & Co., of Chicago. 
Astronomical Photography with Photomicrographic Apparatus.§ — 
Dr. A. C. Mercer obtained photographs of the partial eclipse of the sun 
seen at Syracuse, N.Y. on Oct. 20, 1892. The heliostat and a portrait 
lens of 8 in. focus were arranged to throw a stationary image of about 
1/12 in. diameter of the sun’s disc in the plane usually occupied by the 
object on the stage of the Microscope. This image was projected by a 
1J in. Microscope objective to form a second image, 2§ in. diameter, on 
the ground-glass of the camera. As far as compactness is concerned, this 
arrangement is more convenient than telescopic methods, but it is in- 
ferior in illumination and separating power. The results obtained are 
* Trans. Amer. Micr. Soc , xviii. (1897) pp. 107-16. f Tom. cit., pp. 136-41. 
X Cf. this Journal, 1896, p. 126. 
§ Trans. Amer. Micr. Soc., xviii. (1897) pp. 132-5 (2 figs.). 
