Personal Identification and Description 181
memoir (see our p. 164). Unfortunately he uses the letter j throughout his Plate 11 (our Fig. 32) for what he terms u in the text.
"The divergent ridges that bound any simple pattern admit of nine, and only nine, distinct variations in the first part of their course. The bounding ridge that has attained the summit of any such pattern must have arrived either from the Inner plot (I) [radial delta], the Outer plot [ulnar delta], or from both. Similarly as regards the bounding ridge that lies at the lowest point of the pattern. Any one of the three former events may occur in connection with any of the three latter events, so that they afford in all 3 x 3, or nine possible combinations. It is convenient to distinguish them by easily intelligible symbols. Thus, let i signify a bounding line which starts from the point 1, whether it proceeds to the summit or to the base of the pattern; let o be a line that similarly proceeds from 0, and let J j be a line that unites the two plots [deltas] I and 0 either by summit or by base. Again let two symbols be used, of which the first shall always refer to the summit, and the second to the base of the pattern. Then the nine possible cases are jj, ji, jo; ij, ii, io; oj, oi, oo. The case of the arches is peculiar, but they may be fairly classed under the symbol jj." Finger Prints, pp. 80-81, with j as in figure replacing u of Galton's own text.
Galton next refers to measurements on the print and states that the average ridge interval should be taken as unit of measurement for comparative
Fig. 33. Illustrations of Ambiguities in minutiae, a may appear as b or c, d as e or f.
purposes, especially where prints of non-adults are concerned. Plate 11 (our Fig. 33) gives illustrations of ambiguities in minutiae to which we have previously referred (see our p. 165).
Chapter VI (pp. 89-99) deals with Persistence. It is an extension of the evidence partially given in the Phil. Trans. memoir (see our p. 166 and Plates VII and VIII). Galton has here studied between twenty and thirty different digits and compared minutiae to the number of 700 (p. 96) and only found the one discrepancy to which reference has already been made (see last lines on our p. 166). We reproduce Galton's Plates 13 and 14 (our Plates XVI and XVII) as an illustration of his methods of comparing minutiae, and of the periods for which persistency was demonstrated. Galton again emphasises that it is in the minutiae, not in the measurements of the pattern, that persistency lies (p. 98). After indicating that for the four periods of life there is no change, and that we may expect in 700 minutiae only one to fail us, Galton continues
"Neither can there be any change after death, up to the time when the skin perishes through decomposition ; for example, the marks on the fingers of many Egyptian mummies, and on the paws of stuffed monkeys, still remain legible. Very good evidence and careful inquiry is thus seen to justify the popular idea of the persistence of finger markings, that has hitherto been too rashly jumped at, and which wrongly ascribed the persistence to the general appearance of the pattern, rather than to the minutiae it contains. There appear to be no external bodily characteristics, other than deep scars and tattoo marks, comparable in their persistence to these