348 



Mr. Francis Gal ton 



[May 25, 



Fig. 2. 



Fig. 3. 



each of them shall be included between the double borders of one, 

 two, or some small number of standard portraits, such as Fig. 3. I 

 am as yet unprepared to say how near together the double borders of 

 such standard portraits should be drawn ; in other words, what is the 

 smallest number of grades of unlikeness that we 

 can satisfactorily deal with. The process of 

 sorting profiles into their proper classes and of 

 gradually building up a well-selected standard 

 collection, is a laborious undertaking if attemj)ted 

 by any obvious way, but I believe it can be 

 effected with comparative ease on the basis of 

 measurements, as will be ex2)lained later on, and 

 by an apparatus that will be described. 



Classification of Sets of Measures. — Prisoners 

 are now identified in France by the measures of 

 their heads and limbs, the set of measures of 

 each suspected person being compared with the 

 sets that severally refer to each of many thou- 

 sands of convicts. This idea, and the practical 

 application of it, is due to M. Alphonse Bertillon. The actual method 

 by which this is done is not all that could be theoretically desired, 

 but it is said to be effective in action, and enables the authorities 

 quickly to assure themselves whether the suspected person is or is 

 not an old malefactor. The primary measures in the classification 

 are four — namely, the head length, head breadth, foot length, and 

 middle-finger length of the left foot and hand respectively. Each of 

 these is classified according as it is large, medium or small. There 

 are thus three, and only three, divisions of head lengths, each of which 

 is subdivided into three divisions of head breadth ; again, each of 

 these is further subdivided into three of foot length, and these again 

 into three of middle-finger length ; thus the number of primary classes 

 is equal to three multiplied into itself four times — that is to say, their 

 number is eighty- one, and a separate pigeon-hole is assigned to each. 

 All the exact measures and other notes on each criminal are written 

 on the same card, and this card is stored in its approjDriate pigeon-hole. 

 The contents of each pigeon-hole are themselves sub-sorted on the 

 same principle of three-fold classification in respect to other measures. 

 This process can, of course, be extended indefinitely, but how far it 

 admits of being carried on advantageously is another question. The 

 fault of all hard-and-fast lines of classification, when variability is 

 continuous, is the doubt where to place and where to look for values 

 that are near the limits between two adjacent classes. Let us take 

 Stature as an illustration of what must occur in every case, and let 

 us represent its distribution by what I have called a " Scheme," as 

 shown in Fig. 4. 



Here the statures of any large group of persons are represented 

 by lines of proportionate length. The lines are arranged side by 

 side at equal distances apart on a base, A B, of convenient length. 



