48 POPULAR SCIENCE MONTHLY. 



for purposes of study and comparison. Numerous methods of prepar- 

 ing such records have been elaborated at length by Mr. Francis Galton 

 whose eminent labors upon the comparison and classification of the 

 apical patterns have resulted in an elaborate and accurate system of 

 personal identification, and for these the reader is referred to Chapter 

 III. of his ' Finger Prints. '* The method found by the present author 

 to be the most practicable is a slight modification of Galton 's printing- 

 ink method and may be best explained by a quotation from a set of 

 direction prepared for the use of those willing to assist him in the 

 collection of prints. 



The method of printing is a simple one, the only needful apparatus being 

 (a) a tube of best quality black mimeograph ink, (6) a rubber roller six 

 inches long, such as is sold with photographic outfits, and (c) white, un- 

 ruled paper of a suitable size and quality. A large slate for spreading the ink 

 is a useful accessory, but a smooth sheet of paper pasted upon a flat board 

 or piece of cardboard will fulfil the requirements in this particular. 



In printing, a bit of ink should first be squeezed from the tube upon 

 the slate or other surface used and should be spread evenly by rolling the 

 rubber roller back and forth in various directions, until a thin layer of uni- 

 form thickness is spread over the flat surface. When the surface is in exactly 

 the right state the palm or sole to be printed should first be wiped dry and 

 applied to it, pressing it down from above and taking care not to move 

 it from its original position. The pressure should be applied especially 

 to all regions which, like the center of the palm, are naturally raised above the 

 level of the other parts, and the fingers should be spread a little apart and 

 pressure applied between them. In removing the member from the inked sur- 

 face hold the corners of the latter and lift it quickly, beginning at the wrist 

 or heel. By now placing the member in the same position upon a clean piece 

 of paper and by repeating the pressure and other manipulations a print will 

 be obtained. Finally, a little turpentine may be used to clean the roller and 

 the surface of the skin. 



Prints formed by the above methods reproduce the exact course 

 of every papillary ridge and may be studied at ease, drawn upon and 

 compared with one another in ways never possible in the case of the 

 actual surfaces ; besides which, the contrast of the black ridges with the 

 white interstices (white if the ink has not been used too plentifully) 

 causes the markings to show with far greater distinctness than when 

 presented in the uniform tints of the natural flesh. 



In order, however, that such a print should furnish much instruc- 

 tion, it should be interpreted, that is, mapped out morphologically into 

 its natural areas, a proceeding which is always the first step in the study 

 and which causes the prints to appear somewhat as in the examples 

 given in Fig. 6. In the case of the hand, such an interpretation should 

 begin by the determination of five fixed points, or tri-radii, four of 

 which, the palmar tri-radii, are below the bases of the four fingers and 



* Published by Macmillan & Co., 1892. 



