These plots form corner-stones to my system of outlining and subsequent classification; it is therefore extremely important that a sufficient area of the finger should be printed to include them. This can always be done by slightly _rolling_ the finger (p. 39), the result being, in the language of map-makers, a cylindrical projection of the finger (see Plate 5, Fig. 9, _a-h_). Large as these impressions look, they are of the natural size, taken from ordinary thumbs.
FIG. 9. EXAMPLES OF OUTLINED PATTERNS (The Specimens are rolled impressions of natural size).]
_The outlines._--The next step is to give a clear and definite shape to the pattern by drawing its outline (Fig. 9). Take a fine pen, pencil, or paint brush, and follow in succession each of the two diverging ridges that start from either plot. The course of each ridge must be followed with scrupulous conscientiousness, marking it with a clean line as far as it can be traced. If the ridge bifurcates, always follow the branch that trends towards the middle of the pattern. If it stops short, let the outline stop short also, and recommence on a fresh ridge, choosing that which to the best of the judgment prolongs the course of the one that stopped. These outlines have an extraordinary effect in making finger markings intelligible to an untrained eye. What seemed before to be a vague and bewildering maze of lineations over which the glance wandered distractedly, seeking in vain for a point on which to fix itself, now suddenly assumes the shape of a sharply-defined figure. Whatever difficulties may arise in classifying these figures, they are as nothing compared to those experienced in attempting to classify unoutlined patterns, the outlines giving a precision to their general features which was wanting before.
After a pattern has been treated in this way, there is no further occasion to pore minutely into the finger print, in order to classify it correctly, for the bold firm curves of the outline are even more distinct than the largest capital letters in the title-page of a book.
A fair idea of the way in which the patterns are distributed, is given by Plate 6. Eight persons were taken in the order in which they happened to present themselves, and Plate 6 shows the result. For greater clearness, colour has been employed to distinguish between the ridges that are supplied from the inner and outer sides of the hand respectively. The words right and left _must be avoided_ in speaking of patterns, for the two hands are symmetrically disposed, only in a reversed sense. The right hand does not look like a left hand, but like the reflection of a left hand in a looking-glass, and _vice versa_. The phrases we shall employ will be the _Inner_ and the _Outer_; or thumb-side and little-finger side (terms which were unfortunately misplaced in my memoir in the _Phil. Trans._ 1891).