1879.] on Generic Images. 163 



portraits out of heterogeneous elements, for if the attempt be made to 

 do so the result is monstrous and meaningless. 



It might be expected that when many different portraits are fused 

 into a single one, the result would be a mere smudge. Such, however, 

 is by no means the case, under tlie conditions just laid down, of a 

 great prevalence of the mediocre characteristics over the extreme ones. 

 There are then so many traits in common, to combine and to rein- 

 force one another, that they prevail to the exclusion of the rest. All 

 that is common remains, all that is individual tends to disappear. 



The first of the conii^osites exhibited on this occasion is made by 

 conveying the images of three separate portraits by means of three 

 separate magic lanterns uj^on the same screen. The stands on which 

 the lanterns are mounted have been arranged to allow of nice adjust- 

 ment. The composite about to be shown is one that strains the powers 

 of the process somewhat too severely, the portraits combined being 

 those of two brothers and their sister, who have not even been photo- 

 graphed in precisely the same attitudes. Nevertheless, the result is 

 seen to be the production of a face, neither male nor female, but more 

 regular and handsome than any of the component portraits, and in 

 which the common family traits are clearly marked. Ghosts of 

 portions of male and female attire, due to the peculiarities of tho 

 sej)arate portraits, are seen about and around the composite, but they 

 are not sufficiently vivid to distract the attention. [This effect is well 

 seen in the composite of Napoleon in the autotype photographic plate 

 here annexed.] If the number of combined portraits had been large, 

 these ghostly accessories would have become too faint to be visible. 

 [See the very faint indication of the various ears in the co-composite 

 of the criminals.] 



The next step is to compare this portrait of two brothers and 

 their sister which has been composed by optical means before the eyes 

 of the audience, and concerning the truthfulness of which there can 

 be no doubt, with a photograj)hic composite of the same group. This 

 latter has been made by the process described in the memoir already 

 referred to, and which is analogous to that by which memories are 

 blended. The portraits to be combined are adjusted very carefully 

 one in front of the other, so that the features shall be as exactly 

 superimposed as is possible from the nature of the case. [This is 

 done by making two pin-holes in the bottom of one of them, then 

 placing it on each of the others in succession when held before a strong 

 light, so that the tw^o are seen in transparency, and j)ricking each 

 through the same pin-holes. These pricks serve as fiducial marks for 

 their subsequent arrangement.] The packet of adjusted portraits is 

 next placed in front of the object-glass of a photographic camera, and 

 the portraits are then removed one by one. Thus the impression left 

 on the sensitised plate is that of a succession of different portraits 

 thrown one on the top of another on the same part of it. The result 

 is a composite portrait. A photographic composite prepared in this 

 way from the portraits of the two brothers and sister is now placed in 



