Whoever desires to occupy himself with finger prints, ought to give much time and practice to drawing outlines of different impressions of the same digits. His own ten fingers, and those of a few friends, will furnish the necessary variety of material on which to work. He should not rest satisfied until he has gained an assurance that all patterns possess definite figures, which may be latent but are potentially present, and that the ridges form something more than a nondescript congeries of ramifications and twists. He should continue to practise until he finds that the same ridges have been so nearly followed in duplicate impressions, that even in difficult cases his work will rarely vary more than a single ridge-interval.

When the triangular plot happens not to be visible, owing to the print failing to include it, which is often the case when the finger is not rolled, as is well shown in the prints of my own ten digits on the title-page, the trend of the ridges so far as they are seen, usually enables a practised eye to roughly estimate its true position. By means of this guidance an approximate, but fairly correct, outline can be drawn. When the habit of judging patterns by their outlines has become familiar, the eye will trace them for itself without caring to draw them, and will prefer an unoutlined pattern to work upon, but even then it is essential now and then to follow the outline with a fine point, say that of a penknife or a dry pen.

In selecting standard forms of patterns for the convenience of description, we must be content to disregard a great many of the more obvious characteristics. For instance, the size of generally similar patterns in Fig. 10 will be found to vary greatly, but the words large, medium, or small may be applied to any pattern, so there is no necessity to draw a standard outline for each size. Similarly as regards the inwards or outwards slope of patterns, it is needless to print here a separate standard outline for either slope, and equally unnecessary to print outlines in duplicate, with reversed titles, for the right and left hands respectively. The phrase “a simple spiral” conveys a well-defined general idea, but there are four concrete forms of it (see bottom row of [Plate 11], Fig. 17, oj, jo, ij, ji) which admit of being verbally distinguished. Again the internal proportions of any pattern, say those of simple spirals, may vary greatly without affecting the fact of their being simple spirals. They may be wide or narrow at their mouths, they may be twisted up into a point ([Plate 8], Fig. 14, 52), or they may run in broad curls of uniform width (Fig. 14, 51, 54). Perhaps the best general rule in selecting standard outlines, is to limit them to such as cannot be turned into any other by viewing them in an altered aspect, as upside down or from the back, or by magnifying or deforming them, whether it be through stretching, shrinking, or puckering any part of them. Subject to this general rule and to further and more particular descriptions, the sets ([Plates 7] and [8], Figs. 11, 12, 13) will be found to give considerable help in naming the usual patterns.

PLATE 7.

Fig. 11.
ARCHES.

Fig. 12.
LOOPS.


8
(See Arches, 2.)
9
Nascent Loop.
10
Plain Loop.
11
Invaded Loop.

12
Tented Loop.
13
Crested Loop.
14
Eyeletted Loop.
15
(See Whorls, 21.).

16
Twined Loop.
17
Loop with nascent curl.
18
(See Whorls, 21.)
19
(See Whorls, 22.)