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OCR Rendition - approximate
8 2 FINGER PRINTS CHAP. cation. The resource against uncertainty in respect to ambiguous or difficult patterns is to compile a dictionary of them, with the heads under which it is advisable that they should severally be classed. It would load these pages too heavily to give such a dictionary here. Moreover, it ought to be revised by many experienced eyes, and the time is hardly ripe for this ; when it is, it would be no difficult task, out of the large number of prints of separate fingers which for instance I possess (some 15,000), to make an adequate selection, to enlarge them photographically, and finally to print the results in pairs, the one untouched, the other outlined and classified. It may be asked why ridges are followed and not furrows, the furrow being the real boundary between two systems. The reply is, that the ridges are the easiest to trace ; and, as the error through following the ridges cannot exceed one-half of a ridge-interval, I have been content to disregard it. I began by tracing furrows, but preferred the ridges after trial. Measurements. It has been already shown that when- both plots are present (Plate 4, Fig. 8, 4), they form the termini of a base line, from which any part of the pattern may be triangulated, as surveyors would say. Also, that when only one plot exists (3), and the pattern has an axis (which it necessarily has in all ordinary ii and oo cases), a perpendicular can be let fall upon that axis, whose intersection with it will serve as a second point of reference. But our methods must not be too refined. The centres of the plots are not determinable with real exactness,
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