SCIENTIFIC S EMMAS' 
117 
about the -^th 0 f an inch thick, separated by strips of the same thickness, 
and cemented with marine glue. One corner of the upper plate is removed, 
and a very small hole is drilled through the plate at the comer of the space, 
to be covered by a piece of thin glass placed over the object, whose growth is 
to be watched. The slide is filled with water by means of a pipette applied 
to the open comer, and when the covering glass is placed over the little hole, 
water slowly oozes through by capillary attraction. By this means an object 
may be kept moist for a period of three days. — Yide Silliman’s American 
Journal, September. 
Photomicrographs taken with a Common Landscape Camera. — Mr. J ohn 
Bockett, in a letter to the British Journal of Photography, describes how, 
with the above apparatus, he has taken photographs of the exuvia of the 
spider, skin of the caterpillar, leg of the beetle, &c. The following is 
Mr. Bockett’s description “In the first place, we have the lens, which is 
mounted on a piece of brass tubing about three inches long, having a fine 
screw thread, say for two inches, cut thereon. This screw acts as a fine 
movement, and should be made to work in the flange smoothly and evenly. 
Our next step is the camera, which is constructed to receive the focussing 
screen, and back of an old quarter plate walnut-wood one, already used as a 
general hack. This was made in two parts — 1st, a box 10 inches long, which 
was cut in two, the front portion taking the lens, and the back the focussing- 
glass and dark slide ; and fitted into their two portions is a smaller box — say 
16| inches long — the whole being knocked up out of three-eighths deaL Of 
course the whole of the interior is blackened with lamp-black and shellac, 
mixed and dissolved in methylated spirit. Having fitted our lens to the 
eamera to keep all square, a wooden way is constructed, along which it is 
possible to glide the camera, acting thus as a rough adjustment. In this way, 
which is thirty-six; inches long, at about four inches from the end, is what I 
call the adjustable object-holder, made as follows — Apiece of brass is turned 
so as to have a flange and v screw to fasten it to the tray ; a hole is bored 
through it, in which is soldered a stout piece of brass tube, having a hole, 
with a screw, tapped in its side. In this is fitted a binding-screw, so as to 
grip the object-holder now about to be described. This consists of a piece of 
very thick brass wire, having a screw cut on it at one end, on which is fitted 
a brass cup filled with compressed cork : several of different sizes, from a 
quarter to two inches, should be in stock. In addition to this, if it be in- 
tended to photograph microscopical slides, I made an object-holder, consisting 
of a piece of tin cut of this shape ; at the point a small piece of brass wire 
is soldered, and the tin bent upon itself. This must be dead-blacked. In 
the middle of this is then soldered a small pin, whereby the holder is thrust 
into the cork of the ordinary brass cup before alluded to. It will thus be 
seen that the object can be raised or depressed at will, and by drawing lines 
upon the ground glass of the screen, perfect parallelism can be obtained. 
Behind, or rather, I should say, in front, of this stem and holder is fitted a 
piece of board working on two hinges sixteen inches long by six wide, having 
a clamping screw and brass guide, so as to regulate the reflection of light, and 
■also act as a background to the object. This is covered with white cardboard 
retained in situ 1 by means of drawing-pins. For focussing, two Bamsden 
eye-pieces should be used, one about double the power of the other. By 
