in its middle whenever the component portraits have the same general type of features, and its breadth, or amount of blur, will measure the tendency of the components to deviate from the common type.  This is so for the very same reason that the shot-marks on a target are more thickly disposed near the bull’s-eye than away from it, and in a greater degree as the marksmen are more skilful.  All that has been said of the outlines is equally true as regards the shadows; the result being that the composite represents an averaged figure, whose lineaments have been softly drawn.  The eyes come out with appropriate distinctness, owing to the mechanical conditions under which the components are hung.

[Illustration:  ]

A composite portrait represents the picture that would rise before the mind’s eye of a man who had the gift of pictorial imagination in an exalted degree.  But the imaginative power even of the highest artists is far from precise, and is so apt to be biassed by special cases that may have struck their fancies, that no two artists agree in any of their typical forms.  The merit of the photographic composite is its mechanical precision, being subject to no errors beyond those incidental to all photographic productions.

I submit several composites made for me by Mr. H. Reynolds.  The first set of portraits are those of criminals convicted of murder, manslaughter, or robbery accompanied with violence.  It will be observed that the features of the composites are much better looking than those of the components.  The special villainous irregularities in the latter have disappeared, and the common humanity that underlies them has prevailed.  They represent, not the criminal, but the man who is liable to fall into crime.  All composites are better looking than their components, because the averaged portrait of many persons is free from the irregularities that variously blemish the looks of each of them.

I selected these for my first trials because I happened to possess a large collection of photographs of criminals, through the kindness of Sir Edmund Du Cane, the Director-General of Prisons, for the purpose of investigating criminal types.  They were peculiarly adapted to my present purpose, being all made of about the same size, and taken in much the same attitudes.  It was while endeavouring to elicit the principal criminal types by methods of optical superimposition of the portraits, such as I had frequently employed with maps and meteorological traces,[23] that the idea of composite figures first occurred to me.

[Footnote 23:  Conference at the Loan Exhibition of Scientific Instruments, 1878.  Chapman and Hall.  Physical Geography Section, p. 312, On Means of Combining Various Data in Maps and Diagrams, by Francis Galton, F.R.S.]

The other set of composites are made from pairs of components.  They are selected to show the extraordinary facility of combining almost any two faces whose proportions are in any way similar.