Personal Identification and Description 177 



work had to be done before the mere idea of identification by finger-prints 

 could be transformed into its full realisation as a practical criminal procedure. 

 For that actual transformation we have to thank neither Nehemiah Grew 

 nor Dr Faulds, but Francis Galton expanding and working on the experiences 

 of Sir William Herschel. 



Chapter III (pp. 30-53), entitled Methods of Printing, gives a very 

 full description of methods for the permanent preservation of finger-marks. 



Galton starts by indicating a way of getting very perfect finger-prints, 

 which has been since used very largely for detective purposes. The reader 

 can easily try it for himself; let him pass his finger over the hair at the back 

 of his head, and then press the bulb of his finger on a window pane, that of 

 a recently cleaned window if available; he will find a very perfect imprint of 

 his finger lineation, and there it may remain decipherable for days — under post- 

 war conditions of domestic service! If the finger be merely moistened the 

 impression soon evaporates ; the essential need is to oil the finger very 

 slightly, and this is adequately achieved by the natural oiliness of the hair. 

 Similar finger-prints may be obtained on polished steel — a razor blade — or 

 on table plate. Now-a-days for the purposes of criminal investigation such 

 accidental finger-prints can be reproduced and preserved. Galton next pro- 

 ceeds to give accounts of laboratory and also of pocket apparatus for finger- 

 printing; the important factors are the persistent cleanliness needful in the 

 apparatus, and the extreme thinness of the ink layer on the finger, if a good 

 impression is to be obtained*. This chapter is replete with suggestions such 

 as we have recorded of the younger Galton with his mechanical "dodges." 

 A thin sheet of copper which I found in one of Galton's diaries puzzled me, 

 till I re-read Finger Prints, and there noted that it was to receive soot from 

 a candle (or even a match) to blacken fingers for their prints. 



"Paste rubbed in a very thin layer over a card makes a surface that holds soot firmly, and 

 one that will not stick to other surfaces if accidentally moistened. Glue, isinglass, size, and 

 mucilage, are all suitable. It was my fortune as a boy to receive rudimentary lessons in drawing 

 from a humble and rather grotesque master. He confided to me the discovery, which he claimed 

 as his own, that pencil drawings could be fixed by licking them ; and as I write these words, 

 the image of his broad swab-like tongue performing the operation, and of his proud eyes gleam- 

 ing over the drawing he was operating on, come vividly to remembrance. This reminiscence led 

 me to try whether licking a piece of paper would give it a sufficiently adhesive surface. It did 

 so. Nay, it led me a step further, for I took two pieces of paper and licked both. The dry side 

 of the one was held over the candle as an equivalent to a plate for collecting soot, being saved 

 by the moisture at the back from igniting (it had to be licked two or three times during 

 the process), and the impression was made on the other bit of paper. An ingenious person 

 determined to succeed in obtaining the record of a finger impression can hardly fail altogether 

 under any ordinary circumstances." (pp. 48-9.) 



I should like to have asked Galton what he would have done had there 

 been no paper t ; I feel sure he would have been ready with a substitute ! The 

 chapter concludes with remarks on the photography of finger-prints and on 



* The Galton Laboratory, which collects finger-prints of families, finds that an operator can 

 he easily taught to take decipherable finger-prints with a simple pocket apparatus, which it 

 circulates for this purpose. 



t Quite good impressions can be made with bird lime and candle black, specimens in 

 Galtoniana. 



p Q in 23 



