NATURAL PriILOSOPnY. 147 



would hold the sensitive silver plate, on which the pictures are 

 printed, in perfect, air-tight contact with the negative glass. 

 Every one has noticed that nearly every picture, even among the 

 best, is blurred or indistinct in some of the minute lines. This is 

 because the silver paper was not closely pressed in those parts 

 upon the glass plate. The pad generally used is of felt, the finest 

 of which has small pits and inequalities in its surface. Wherever 

 there is a pit there will be a defect in the picture. If there are 

 100 of these little pits in a square inch, there will be 100 places in 

 tlie picture where the minute lines are not brought out, and hence 

 a blurred appearance. The platen board over the pad is perfectly 

 straight. Now, if the negative glass, on \vhich the pressure is 

 brought, be warped, it is plain that some places will be pressed 

 hard, while others will not be pressed at all, or only lightly. 

 Tlien the picture will come out sharp and clear in the hard-pressed 

 phices and blurred in the others. Such pictures are valueless, and 

 hence there must be great waste of silver paper, as well as of the 

 time of the operator. This invention is designed to take the place 

 of the felt pad in common use. It consists of an elastic bag, made 

 of very tine, soft, and pliable India-rubber, air-tight, in two com- 

 partments, which lap each other by means of an ingeniously ar- 

 ranged suture. This bag may be filled with air, gas, or any fluid. 

 It will be used in the same manner as the old pad. The nega- 

 tive will be laid in the printing-frames, the silver or sensitive 

 paper laid on the negative, next the pad, and then the pressing- 

 board or platen. Every photographer will see at once that the 

 elasticity of the bag will accommodate its surface to that of the 

 negative glass. That is to say, if the glass is convex, the air or 

 fluid in the bag will flow, under the pressure of the platen, to 

 those places which are low, and the surface of the bag will be- 

 come an exact impression or counterpart of the glass surface. 

 No part of the negative's surface, no matter how uneven it may 

 be, can escape the pressure, and the pressure will be exactly equal 

 everywhere. There will be no vacuums between the pad and silver 

 paper, nor between the latter and the negative glass ; hence there 

 will be no discoloration of the silver paper, which always occurs 

 from exposure to air. 



Since the art of photography has been known, hundreds of at- 

 tempts have been made to find a contact pad which would secure 

 the results which Mr. Buchtel claims will invariably follow the use 

 of his invention ; but heretofore without success. It is simple in 

 irs principles of operation, and the only wonder is that it had not 

 been thought of long since. 



PLIABLE GLASS. 



About three months ago we called attention to a new material, 

 which had been introduced in Paris by M. A. Marion, under the 

 above name, possessing valuable qualities for many photographic 

 purposes. 



The " caoutchouc pellicle" is in sheets the size of photographic 



