SCIENTIFIC SUMMAEY 
533 
the reasons why the gradations and details are rendered so perfectly. We 
owe this process to Mr. J. Burgess. 
The Simpsontype. — Far more simple than the preceding, this process gives 
results no less beautiful. A collodion, which dries with perfect transparency, 
contains equal portions of ether and alcohol, and an amount of gun-cotton 
varied according to its quality — six grains usually being sufficient — is 
adopted, and to every ounce of this are added — 
A plate of opal glass, thickly flashed, of a pure creamy-white surface, well 
ground and polished, is coated with the collodio-chloride of silver, and when 
quite dry is placed cautiously in contact with a negative, and printed in the 
usual way, the time of exposure being somewhat less than is required for 
paper prints, but of course varying with the character of the negative and 
that of the light. It is better to over rather than under print, because the 
one may be reduced by a strong solution of cyanide of potassium, or used as 
a transparency, while the under-exposed print is useless for any purpose, and 
is past remedying. When taken from the printing-frame, the proof is toned 
in any one of the alkaline gold-toning solutions used in a weak and old 
condition, and fixed with hyposulphite of soda, 1 oz. in 10 of water. Mr. 
Simpson has been awarded the President’s medal of the Photographic 
Society for this process. 
New Camera Stand. — Mr. Springham introduced at a meeting of the North 
London Photographic Association an improved stand for the camera, of 
which the following is a description, given in the words of the inventor : — 
“ This in.vention is applicable not only to cameras, but also to telescopes and 
other instruments requiring horizontal and vertical motion. It consists of 
the ordinary iron triangle, to two corners of which are fixed two pieces of 
iron curved towards each other, and each having a horizontal slot through 
it in which moves a little iron foot attached to the front part of the camera. 
The other angle of the triangle has a horizontal extension, in which is cut a 
vertical curved slit. In this works a curved screw having two flat sides, and 
which can be moved either vertically or horizontally in the slot, and secured 
in any position by means of two nuts running on it. This screw is attached 
to the hinder part of the camera. The curves of the three slots and the curved 
screw have all one common centre, which enables them to work together. 
Mr. Springham claims for this stand that it is lighter than any other pos- 
sessing similar advantages, firmer, and while easily detached from the camera, 
holds it immovably at aU other times. 
Neiv Air-tight Bath. — Mr. A. G-. Clifton, a gentleman to whom photo- 
graphers owe other iugenious improvements in photographic apparatus, calls 
attention, in a communication to our useful contemporary The Art Student, 
to a new air-tight bath which is a great improvement upon those usually 
made. The appended cut and description will suffice by way of explanation. 
A is the elevation of the ordinary bath, the weak pomts in wliich are at c c, 
which after a little wear, from the great pressure of the screw, F, are apt to 
give. B is the elevation of the improved bath, wiiich instead of the frame- 
Nitrate of silver 
Chloride of strontium 
Citric acid 
2 N 2 
