Intelligence and Miscellaneous Articles. 75 



■will have changed colour, and the odour of acetic acid as well as that 

 of alcohol will have disappeared, and the liquid will have acquired a 

 peculiar but agreeable vinous odour. It is in this state that I prefer 

 to employ it. 



6. Into the iodide thus prepared and modified the plate is dipped 

 for a few seconds. All these operations may be performed by mode- 

 rate daylight, avoiding however the direct solar rays. 



7. A solution is made of nitrate of silver, containing about 70 

 grains to one ounce of water. To three parts of this add two of 

 acetic acid. Then if the prepared plate is rapidly dipped once or 

 twice into this solution it acquires a very great degree of sensibility, 

 and it ought then to be placed in the camera without much delay. 



8. The plate is withdrawn from the camera, and in order to bring 

 out the image it is dipped into a solution of protosulphate of iron, 

 containing one part of the saturated solution diluted with two or 

 three parts of water. The image appears very rapidly. 



9. Having washed the plate with water, it is now placed in a so- 

 lution of hyposulphite of soda, which in about a minute causes the 

 image to brighten up exceedingly by removing a kind of veil which 

 previously covered it. 



10. The plate is then washed with distilled water, and the process 

 is terminated. In order, however, tc guard against future accidents, 

 it is well to give the picture another coating of albumen or of varnish. 



These operations may appear long in the description, but they are 

 rapidly enough executed after a little practice. 



In the process which I have now described, I trust that I have 

 effected a harmonious combination of several previously ascertained 

 and valuable facts — especially of the photographic property of iodide 

 of iron, which was discovered by Dr. Woods of Parsonstown, in 

 Ireland, and that of sulphate of iron, for which science is indebted 

 to the researches of Mr. Robert Hunt. In the true adjustment of 

 the proportions, and in the mode of operation, lies the difficulty of 

 these investigations ; since it is possible by adopting other propor- 

 tions and manipulations not very greatly differing from the above, 

 and which a careless reader might consider to be the same, not only 

 to fail in obtaining the highly exalted sensibility which is desirable 

 in this process, but actually to obtain scarcely any photographic re- 

 sult at all. 



To return, however, from this digression. — The pictures obtained 

 by the above -described process are negative by transmitted light and 

 positive by reflected light. When I first remarked this, I thought 

 it would be desirable to give these pictures a distinctive name, and 

 I proposed that of Amphidjpe, as expressive of their double nature — 

 at once positive and negative. Since the time when I first observed 

 them, the Collodion process has become known, which produces pic- 

 tures having almost the same peculiarity. In a scientific classifica- 

 tion of photographic methods, these ought therefore to be ranked 

 together as species of the same gcaus. These Amphitypc pictures 

 differ from the Dearly related Collodion on— in an important circum- 

 stance, viz. the great hardness of the film and the firm fixation of 

 the image, which is such that in the last washing, No. 10, the image 



