ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
165 
most convenient for ordinary observation, is far too feeble to be visible 
on the focusing-screen of the camera. In the early days of the art, when 
gelatin-bromide plates were yet unknown, direct sunlight was the only 
practicable illumination for anything but the most moderate amplifi- 
cations. 
To secure this a heliostat was indispensable, and it is now more than 
twenty years ago since the writer described in the Monthly Journal 
of this Society a plan in which this necessity was overcome, by em- 
ploying a condenser of such long focus that the image of the sun was 
vivid enough to give one time to insert one’s dark slide and expose 
before it had passed across the object. 
The wet collodion-plate, if not used quickly, was utterly spoiled. 
With the dry plate, on the other hand, apart from its greater sensitive- 
ness, length of exposure is a matter of no moment. The difficulty, how- 
ever, of obtaining adequate light to sufficiently illuminate the ground 
glass remains, and the method I am about to describe overcomes this by 
doing away with the focusing-screen altogether. 
No special camera is required. Almost any quarter-plate or 5 X 4-in. 
landscape camera will serve for the purpose ; but it is most convenient 
to select one with a conical bellows, in which the front is completely 
detachable from the standards that attach it to the base-frame when set 
up for ordinary work. The one I am using is an Adam’s “Victor” 
camera. The movable front carrying the lens is only 2 in. square, and 
a spare one, to receive the collar that is to connect camera and Micro- 
scope, is of course necessary. 
Take a piece of black velvet about 2 in. wide, and have it sewn round 
the draw-tube of the Microscope, not too tightly. Then take a long 
strip of brown paper 1 in. wide dipped in paste or gum, and wind it 
round the middle of the velvet till it is about 1/16 in. thick. When 
this has dried thoroughly, fold down the projecting part of the velvet 
over the outside of the pasteboard tube we have thus made, and sew the 
edges together so as to neatly cover the outside of the tube. Nothing 
more is required but to cut a hole in the spare front just large enough 
to tightly hold the velvet-covered pasteboard tube. If the hole be made 
the right size, the joint will be quite light-tight without any packing or 
cement of any sort. 
The Microscope is always used in the vertical position, and the 
camera is supported above it by means of a telescopic upright jointed 
vertically into a heavy base-board on which the Microscope stands. 
The base-board should be about 1 ft. square, and at least an inch 
thick, standing on four low studs placed at the corners, or, better still, 
with studs at three corners, and the fourth stud replaced by a coarse- 
pitched, blunt-ended screw, so as to allow for inequalities of the surface 
on which it may be placed, as it is important that the apparatus be as 
little liable to vibration as may be. The upright consists of two stout 
drawn metal tubes, sliding one within the other, of such lengths that 
the inner tube can be fixed, by means of a clam ping- screw, at any length 
between 15 and 20 in. The inner or sliding tube ends in a square metal 
plate about 2J in. square, with a central hole large enough to take the 
screw which ordinarily fixes the camera to its tripod. This plate must 
project a little clear of the surface of the tube, so that the base-board 
