COMPOSITE PORTRAITS. 465 



pictures blend perfectly. If taken in a binocular camera for the purpose, each 

 person being taken on one-half of the negative, I am sure the results would be 

 still more striking. Perhaps something might be made of this in regard to the 

 expression of emotions in man and the lower animals, etc. I have not time or 

 opportunities to make experiments, but it seems to me something might be made 

 of this by photographing the faces of different animals, different races of man- 

 kind, etc. I think a stereoscopic view of one of the ape tribe and some low-caste 

 human face would make a very curious mixture ; also in the matter of crossing of 

 animals and the resulting offspring. It seems to me something also might result 

 in photos of husband and wife and children, etc. In any case the results are 

 curious, if it leads to nothing else. Should this come to anything, you will no 

 doubt acknowledge myself as suggesting the experiment, and perhaps send me 

 some of the results. If not likely to come to anything, a reply would much 

 oblige mo. Yours very truly, 



" A. L. Austin, 0. E., F. R. A. S." 



Dr. Carpenter informs me that the late Mr. Appold, the mechani- 

 cian, used to combine two portraits of himself, under the stereoscope. 

 The one had been taken from an assumed stern expression, the other 

 with a smile, and this combination produced a curious and effective 

 blending of the two. 



Convenient as the stereoscope is, owing to its accessibility, for deter- 

 mining whether any two portraits are suitable in size and attitude to 

 form a good composite, it is nevertheless a makeshift and imperfect way 

 of attaining the required result. It cannot of itself combine two images ; 

 it can only place them so that the office of attempting to combine them 

 may be undertaken by the brain. Now the two separate impressions 

 received by the brain through the stereoscope do not seem to me to be 

 relatively constant in their vividness, but sometimes the image seen by 

 the left eye prevails over that seen by the right, and vice ve)'sa. All 

 the other instruments I am about to describe accomplish that which the 

 stereoscope fails to do ; they create true optical combinations. As re- 

 gards other points in Mr. Austin's letter, I cannot think that the use of 

 a binocular camera for taking the tw T o portraits intended to be combined 

 into one by the stereoscope would be of importance. All that is want- 

 ed is that the portraits should be nearly of the same size. In every 

 other respect I cordially agree with Mr. Austin. 



The best instrument I have as yet contrived and used for optical 

 superimposition is a " double-image prism " of Iceland spar. The latest 

 that I have had were procured for me by Mr. Tisley, optician, 172 

 Brompton Road. It has a clear aperture of a square, half an inch in 

 the side, and when held at right angles to the line of sight will separate 

 the ordinary and extraordinary images to the amount of two inches, 

 when the object viewed is held at seventeen inches from the eye. This 

 is quite sufficient for working with carte-de-visite portraits. One im- 

 age is quite achromatic, the other shows a little color. The divergence 

 may be varied and adjusted by inclining the prism to the line of sight. 

 By its means the ordinary image of one component is thrown upon the 



VOL. xiii. 30 



