160 Life and Letters of Francis Galton
system of -finger-print Identification Offices with a common nomenclature, a common method of indexing and a common code.
Realising how such Identification Offices, depending wholly on fingerprinting, now stretch from London to Tokyo, from Tokyo to San Francisco and thence to New York, we see how Galton recognised a widespread need, and how by his ceaseless energy he carried through a great reform. Whatever influence his idea of correlation may have exercised in the field of scientific investigation-and it has been indeed deep and far-reaching-the establishment throughout the world of finger-print identification is a no less astonishing mark of his power of achieving on the practical side.
On October 16, 1902, Galton has still another letter in Nature (Vol. LXVI, p. 606). It is entitled "Finger-Print Evidence." The problem he is concerned with here is to find the best manner of convincing a judge and jury that an accused person is really one whose finger-prints are already on the criminal register. Owing to the courtesy of Scotland Yard he had received two
Fig. 19. Ridge-tracing Method of identifying Finger-Prints.
enlarged photographs of thumb-prints. The first is that of an impression left on the window frame of a house where a burglary had occurred, and the second that of the left thumb of a criminal who had been released and whose finger-prints were preserved and classified at Scotland Yard. Galton applies the method of his Decipherment of Blurred Finger Prints (see our p. 194), " believing that to be the readiest way of explaining to a judge and jury the nature of the evidence to be submitted to them.... The questions of the best mode of submitting evidence and the amount of it that is reasonably required to carry conviction deserve early consideration, for we may have a great deal of it before long." In the accompanying diagrams ' it will be seen that Galton has selected and numbered ten minutiae for identification and comparison. It is scarcely conceivable that any twelve reasonably intelligent men would fail to be convinced of the identity of the two thumb-prints, although conviction would be still further strengthened were a third random thumb-print of the same type presented, which would undoubtedly lack corresponding minutiae.