1857.] Mr, Malone on Photographic Engraving. 343 



the wedge-shaped vessel was exhibited, and it was seen that the 

 orange band became very faint when the solution was deep, and in 

 contrast with the neighbouring brilliant red appeared sometimes 

 green, but more generally violet. Much, in this case also, was 

 found to depend on the eye of the observer ; but that a violet 

 sensation might be produced from orange under such circumstances 

 had been proved by the speaker, who in repeating one of Dr. 

 Tyndairs experiments — that of looking at the daylight through a 

 red glass on which a vermilion wafer was fastened — had frequently 

 seen the wafer assume a violet tint. He believed that these three 

 causes were sufficient to account for all the apparent changes of 

 colour produced in a ray by absorbent media. 



[J. H. G.] 



WEEKLY EVENING MEETING, 



Friday, February 13. 



Sib Benjamin Collins Brodie, Bart., D.C.L. F.R.S. 

 in the Chair. 



Thomas A. Malone, F.C.S. 



DIKECTOB OF THE LABORATOBY IN THE LOKDON INSTITOTIOK. 



On the Application of Light and Electricity to the production 

 of Engravings — Photogalvanography, 



The subject of this discourse is one with which the speaker has been 

 for some years practically acquainted. In 1 844, he experimented 

 for many months upon the engraving process of M. Fizeau of Paris, 

 in conjunction with M. Claudet and M. Fizeau. Since that time he 

 has closely watched all the steps of improvement that have been 

 taken, down to the latest investigations of Talbot, Niepce de St. 

 Victor, Pretsch, and Poitevin. He ventured thus to think himself 

 fairly entitled to lay before the auditory the numerous remarkable 

 and beautiful specimens he had gathered, or kindly been furnished 

 with, accompanied by such commentaries and notices of processes 

 as the time admitted. 



The various methods hitherto devised for the accomplishment of 

 that important problem the certain perpetuation and cheap mul- 

 tiplication — by means of printer's ink and the ordinary printing 

 presses — of the images of natural objects, as obtained in the camera 

 obscura by the processes of ordinary photography, may be arranged 

 under three great divisions. 



