ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
103 
bracket to hold an ordinary Microscope lamp with an attached bull’s- 
eye. Only the bull’s-eye K (one of my doublets) is shown. 
Finally the board A 13 slides in uprights on the base P (not shown) ; 
this is to allow the magnification to be altered by increasing or decreas- 
ing the distance between the objective and the paper on the base-board 
P on which the drawing is to be made. To use the instrument, in the 
first instance the bull’s-eye K is focused to the edge of the lamp flame 
and parallel rays are sent on the mirror M. The condenser suited to 
the power is arranged at D. The distance between K and D should not 
be less than 12 in. Having placed the object in the clips on the stage, 
and having roughly focused the objective, the screw S must be loosened 
and the whole block G H moved up or down so that the rays from the 
condenser are focused on the objective. The field is then limited by 
the wheel of diaphragms. The illumination from an ordinary Micro- 
scope lamp with a 1/2 in. wick will be found sufficient when the appara- 
tus is used in a darkened room, but if scattered light interferes with the 
image, cloth curtains may be provided to shield it off. This instrument 
was shown on the evening of the special exhibition with oxy-hydrogen 
illumination, a miniature jet and zirconium disc being employed, by 
which means sufficient light was obtained although the room was lighted 
by electricity. 
The instrument gives an inverted and transposed image, the draw- 
ing is therefore precisely as it is in nature, which is not the case in some 
cameras which correct the inversion but leave the transposition.” 
(4) Photomicrography. 
Nachet’s large Photomicrographic Apparatus. — In this apparatus, 
represented in fig. 14, the two slide-ways superposed allow of a separa- 
tion of 2 m. between the objective of the Microscope and the sensitive 
plate. The camera, measuring 18 by 24 cm., is divided into two parts 
connected by bellows of equal length. The front portion carries a 
special chamber with which the body-tube of the Microscope makes a 
light-proof connection. In the upper part of this chamber, at 0, there 
is a lid which allows of the adjustment of the projection eye-pieces. 
Exact focusing is effected by means of the rod CT in connection 
with an endless screw E, which engages in the wheel H, placed in 
front of the screw-head of the slow motion, and connected with it by 
a spiral spring of such resistance that the motion may be communicated 
to it instantaneously and without vibration. The connection between 
the rod and tangent screw is of the same kind. The extremity of the 
upper slide is provided with a levelling screw Y to keep it in contact 
with the table on which the apparatus is placed. On this table are 
placed the different illuminating apparatus: heliostat, oxy-hydrogen 
lamp, ordinary lamp, &c. 
Bousfield’s Photomicrography.*— The second edition of this guide 
to the science of photomicrography has just appeared. It has been 
entirely rewritten and much enlarged. It is extremely well got up, and 
the illustrations, including specimens of photomicrography, are frequent. 
For those more interested in photographing histological and bacterio- 
* J. and A. Churchill, London, 1892, pp. 174, 34 figs, and 1 pi. 
