The series of 30 imaginative outline profiles were taken from Havelock Ellis' book on "The Criminal," wherein it is stated that they were "reproduced from sketches made by Dr. Vans Clarke at the model prison of Pentonville," and that the heads they depict are "by no means very exceptional, and represent at the least 10 per cent. of the criminals examined." Dr. Clarke also affirmed that "the sketches were necessarily taken in haste, but they were true, and were considered to be successful as likenesses"; and adds that he "was compelled to make a selection rather from want of time than from the lack of material." In the above reproductions, the only modification on the original drawings is that the distance between the base of the nose (nasion), and the centre of the ear (i.e., of the auditory meatus), has been made of the same length in each outline: a modification which was necessary for constructing the composite portrait as presented above.
The series of 30 photographic outline profiles were traced from a corresponding series of photographs which were selected at random from the official stock of portraits at Parkhurst. Through the medium of a lantern, the photographs were enlarged on a screen, to a scale giving the same distance, between the base of the nose and the centre of the ear, in each outline; and the tracings, thus obtained, were subsequently reduced by photography to the dimensions presented above.
The composite portraits consist of the corresponding 30 outlines superimposed. This was achieved by tracing them successively, one on the top of the other, through carbon paper; each outline having been first adjusted so that the line between the nasion and the centre of the ear lay exactly in the same position.
An examination of these contrasted outlines shows most strikingly the difference between "criminal types," as registered by the mechanical precision of a camera, and as viewed by the imagination of an enthusiastic, but uncritical, observer.