468 THE POPULAR SCIENCE MONTHLY. 



their catching no more than a single expression. If many photographs 

 of a person were taken at different times, perhaps even years apart, 

 their composite would possess that in which a single photograph is 

 deficient. I have already pointed out the experience of Mr. Appold to 

 this effect. The analytical tendency of the mind is so strong that, out 

 of any tangle of superimposed outlines, it persists in dwelling prefer- 

 ably on some one of them, singling it out and taking little heed of the 

 rest. On one occasion it will select one outline, on another a different 

 one. Looking at the patterns of the papered walls of our room we 

 see, whenever our fancy is active, all kinds of forms and features ; we 

 often catch some strange combination which we are unable to recall on 



CD 



a subsequent occasion, while later still it may suddenly flash full upon 

 us. A composite portrait would have much of this varied suggestive- 

 ness. 



A further use of the process would be to produce, from many inde- 

 pendent portraits of an historical personage, the most probable likeness 

 of him. Contemporaneous statues, medals, and gems, would be very 

 suitable for the purpose, photographs being taken of the same size, 

 and a composite made from them. It will be borne in mind that it is 

 perfectly easy to apportion different "weights " to the different compo- 

 nents. Thus, if one statue be judged to be so much more worthy of 

 reliance than another that it ought to receive double consideration in 

 the composite, all that is necessary is to double either the time of its 

 exposure or its illumination. 



The last use of the process that I shall mention is of great interest 

 as regards inquiries into the hereditary transmission of features, as it 

 enables us to compare the average features of the product with those 

 of the parentage. A composite of all the brothers and sisters in a 

 large family would be an approximation to what the average of the 

 product would probably be if the family were indefinitely increased in 

 number, but the approximation would be closer if we also took into 

 consideration those of the cousins who inherited the family likeness. As 

 regards the parentage, it is by no means sufficient to take a composite 

 of the two parents ; the four grandparents and the uncles and aunts 

 on both sides should be also included. Some statistical inquiries I 

 published on the distribution of ability in families ' give provisional 

 data for determining the weight to be assigned in the composite to 

 the several degrees of relationship. I should, however, not follow 

 those figures in the present case, but would rather suggest for the 

 earlier trials, first to give equal " weights " to the male and female 

 sides ; thus the father and a brother of the male parent would count 

 equally with the father and a brother of the female parent. Secondly, 

 I should " weight " each parent as 4, and each grandparent and each 

 uncle and aunt as 1 ; again, I should weight each brother and sister as 

 4, and each of those cousins as 1 who inherited any part of the like- 

 1 " Hereditary Genius," p. 317. Column D. Macmillan, 1869. 



