Page:Popular Science Monthly Volume 63.djvu/398

394 hundred thousand which it would be necessary to look over carefully in comparing with a certain definite case would average about five.

The data necessary for this latter comparison are abundantly furnished by the details of the individual ridges, termed by Galton the 'minutiæ' and the farther description and subdivision of the records by means of these he terms the Secondary classification. These and other useful details are appended to the formulæ given above by means of 'descriptive suffixes' arbitrarily selected and described in a table, a copy of which must, of course, be always at hand, at least until it be thoroughly committed to memory by the clerk in charge of the records. The nature of these suffixes and of the details which they describe may be learned from the following examples, taken at random from Galton's table:

The implied suggestion of 'x' brings up a question which probably occurs to the reader at about this time, namely, whether a pattern is ever of a mixed type, or half way between two, thus giving a chance for a difference of interpretation and a consequent embarassment in finding the case from the formula. This certainly occurs occasionally, but Galton has well disposed of the difficulty by comparing it to the doubt experienced when consulting a city directory for a Scotch name beginning with 'Mac,' variously written, either in full or as Mc or M', and classed differently by various lexicographers. In both cases the investigator, failing to find what he desires in one place, looks in another, and neither here nor there is the difficulty a serious one.

Each finger tip record is placed on a card measuring 12 x 5 inches, and contains, when complete, rolled impressions of the ten digits, a set of 'dab' impressions of the four fingers of each hand (as duplicates for comparison) and, at the right hand upper corner, the formula. In Scotland Yard a folded paper is used instead of a card, and the arrangement of the prints differs somewhat from the above.

Concerning the practical adoption of the Galton system at present, it is hard to get details, but the recommendation of the English committee in 1894 has been referred to, and it seems that since that time the method has come into quite general use in England. It is of course impossible to devise a method which in every detail will be perfect from the start, and as Mr. Galton is continually at work upon his system, the improvements suggested both by him and by those practically engaged in the work can not fail to modify details until it is brought to the highest degree of efficiency.