196 Life and Letters of Francis Galton 



is drawn from the minutiae and not from the general pattern ; for though no 

 one can mistake a decided whorl for a decided loop, lesser differences are often 

 deceptive to the untrained eye, especially when only a portion of the pattern 

 has been impressed. 



But the chief interest of Gal ton's present work lies not in the identification 

 of poor impressions at fourteen years' interval by aid of their minutiae but 

 in his manner of presenting the evidence. His aim is to show that rough 

 impressions such as may be taken by ordinary officials (or left behind by the 

 burglar) can be made to afford evidence strong enough to convince a jury 

 that two finger-prints had been made by the same person. "It is of course 

 supposed that the cogency of the finger-print argument will be presented to 

 the jury in that lucid and complete form in which it is the business of barristers 

 to state and support their case, when they are satisfied of the integrity of 

 the evidence on which it is based" (p. 2). Galton's method is best grasped 

 from his plates rather than from a verbal description. He first enlarges his 

 prints 2^ times photographically. The enlargements, eight to the page, occupy 

 Plates I-IV. These give him a general impression of the patterns, and the 

 particular cases and the parts of the particular cases he considers it desirable 

 to study further. These selected parts of particular cases are now photo- 

 graphically enlarged to seven times natural size. These enlargements occupy 

 Plates V-VIII, and are printed in black. Thus far the work, except for the 

 choice of parts, has been largely mechanical. Now comes the labour of the 

 expert: the outlining of the ridges on these blurred prints. In doing this 

 tracing paper may be used by the draughtsman, but Galton thinks a better 

 plan is to do the outlining on the back of the print placed against a pane of 

 the window or on a photographic retouching frame. 



"The axes should be drawn with a finely-pointed pencil, and with care, down the middle 

 of the ridges. Slap-dash attempts are almost sure to be failures. It is advisable to take pains 

 to determine a common starting point, before proceeding to draw any lines at all ; then to 

 proceed from point to point in the two prints alternately, at first with wariness but afterwards 



much more freely The continuous course of every line has to be made out from beginning 



to end, and the lines must nowhere be too crowded or too wide apart, and they must all flow 

 in easy and appropriate curves ; also as much regard must be paid to such blanks as are not 

 obviously due to bad printing as to the markings. The general effect of these conditions is that 

 a mistake in deciphering any one part of the impression nearly always introduces confusion at 

 some other part, where the lines refuse to fit in." (pp. 10-11.) 



On Plates IX-XII Galton gives his outlinings, the blurred ridges being 

 now printed in orange with the outlining in black, still on a sevenfold scale. 

 Tiny circles mark the ends or beginnings of ridges, but as Galton warns his 

 readers some of these may well be forks (see his p. 8 and our pp. 165, 181). 



Lastly Galton provides on the same sevenfold scale the outlinings of the 

 ridges without the blurred ridges at all. Here in the juxtaposed prints 

 corresponding minutiae are given the same small numbers, so that it is 

 perfectly easy to refer to one after another of the correspondences. The whole 

 series of plates forms a singularly lucid illustration of what it is possible to 

 do even with badly printed and partial impressions. No reasonably thought- 

 ful counsel ought with such evidence to fail to convince a jury that Dwarika 



