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OCR Rendition - approximate
3 2 FINGER PRINTS CHAP. combined in equal degrees the result must be a plain black blot. The following explanations will be almost entirely confined to the first method, namely, that of ordinary printing, as the second method has so far not given equally good results. The ink used may be either printer's ink or water colour, but for producing the best work, rapidly and on a large scale, the method of printer's ink seems in every respect preferable. However, water colour suffices for song e purposes, and as there is so, much convenience in a pad, drenched with dye, such as is commonly used for hand stamps, and which is always ready for use, many may prefer. it. The processes with printer's ink will be described first. The relief formed by the ridges is low. In the fingers of very young children, and of some ladies whose hands are rarely submitted to rough usage, the ridges are exceptionally faint ; their crests hardly rise above the furrows, yet it is the crests only that are to be inked. Consequently the layer of ink on the slab or pad on which the finger is pressed for the purpose of blackening it, must be very thin. Its thickness must be less than half the elevation of the ridges, for when the finger is pressed down, the crests displace the ink immediately below them, and drives it upwards into the furrows which would otherwise be choked with it. It is no violent misuse of metaphor to compare the ridges to the crests of mountain ranges, and the depth of the blackening that they ought to receive,
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