178 Life and Letters of Francis Galton
cmethods of enlarging them. In the Galtoniana -we have still his special amera for enlarging finger-prints (see our p. 215), his much enlarged series of finger-prints used for fine classification reproduced for this work, and to be found in a pocket at the end of this volume) and the watchmaker's glass mounted on a stand for directly examining them*.
Chapter IV (pp. 54-63) deals with The Ridges and their Use. Galton starts with the ridges of the palm of the hand, and indicates that they are not very closely related to the "creases," so that the latter cannot be the cause of the former. He also refers to the ridges on the soles and toes, but ultimately confines his attention to those on the fingers. Here he defines two important terms: first, Minutiae, which are the minute peculiarities characterising an individual ridge. A ridge may divide into two or unite with another (see Fig. 31, a and b), or it may divide and almost immediately
Chaxazferistia Peeuharil'ies it2 Ridges.
about 8 times the natural sir) Fig. 31.
reunite, enclosing a small circular or elliptic space (c) ; at other times it may begin or end abruptly (d and e); or lastly the ridge may be so short as to form a small island (f). Secondly, Patterns: whenever an interspace is left between the boundaries of different systems of ridges, it is filled by a small system of its own which will have some characteristic shape. This shape is termed a pattern (see Figs. 20, 21 on our pp. 162, 163). The descriptions of minutiae and of patterns belonging to an individual are of special value for the purposes of identification.
On the whole there is little known of the origin and use of the ridges, beyond the fact that they carry the sweat pores. Nor is their origin or use of much importance for the purpose of identification provided we can be assured of their persistency during life. Titchener, as I have noted (p. 168), made, at the suggestion of Galton, a series of experiments with the aesthesiometer, and proved that the fineness or coarseness of the ridges in different persons had no effect whatever on the delicacy of their tactile discrimination.
* This finger-print glass appears in Furse's painting of Galton; seee the Frontispiece to Vol. i. It is worth noting that Galton selected this piece of-apparatus as the most characteristic of his many activities.