28 HOUSE, GARDEN, AND FIELD 



thin paper against some part of your own skin, and then 

 stroke the paper with the point of a pin. The movement 

 of the point can be felt through the paper, though paper 

 cannot feel, and in the same way we can feel pressure 

 through the epiderm, though it can no more feel than the 

 paper itself. 



The skin of the finger- tip shows a special pattern, which 

 can be made very evident by pressing it first on a plate 

 spread with printer's ink, and then on white paper. 1 After 

 a few trials we get a sharp impression or print of the 

 finger-tip. There is a central point, round which a great 

 number of lines are arranged, so as to form either spiral 

 or concentric figures. Each line is a ridge, with a steep 

 slope facing the centre, and a broad slope facing outwards. 

 The ridges sometimes branch or run out to a point, and 

 new ones come in, so that the arrangement is not per- 

 fectly regular. All these details can be seen by carefully 

 examining a finger-print, or better still by studying the 

 finger-tip itself with a good lens. 



1 To get good and sharp impressions some trouble must be taken. The 

 necessary appliances can be borrowed from a printer. The ink should be 

 more fluid than is used for letter-press printing, and must be spread out on 

 a slab of glass or polished copper with a small printer's roller. Pains must 

 be taken to get a very thin and uniform layer ; it is best to begin with 

 very little ink, and add more if required. " The right hand of the subject, 

 which should be quite passive, is taken by the operator, and the bulbs 

 of his four fingers laid flat on the inked slab, and pressed gently but 

 firmly on it by the flattened hand of the operator. Then the inked fingers 

 are laid flat upon the upper part of the right hand side of the card, and 

 pressed down gently and firmly, just as before, by the flattened hand of 

 the operator. This completes the process for one set of prints of the four 

 fingers of the right hand. Then the bulb of the thumb is slightly rolled on 

 the inked slab, and again on the lower part of the card, which gives a 

 more extended but not quite so sharp an impression. Each of the four 

 fingers of the same hand, in succession, is similarly rolled and impressed. 

 This completes the process for the second set of prints of the digits of the 

 right hand. Then the left hand is treated in the same way" (Galton). 

 By laying a sheet of thin paper on a pad, and pressing the inked hand 

 upon it from the wrist to the finger-tips, a print of the whole palm can be 

 taken. The fingers can be cleansed by turpentine. Indian ink, rubbed 

 thick and black, will do, but not so well as printer's ink. 



