Differences between finger prints of different classes might continue to exist although those of different races are inconspicuous, because every race contains men of various temperaments and faculties, and we cannot tell, except by observation, whether any of these are correlated with the finger marks. Several different classes have been examined both by Mr. Collins and myself. The ordinary laboratory work supplies finger prints of persons of much culture, and of many students both in the Art and in the Science schools. I took a large number of prints from the worst idiots in the London district, through the obliging assistance of Dr. Fletcher Beech, of the Darenth Asylum; my collections made at Board Schools are numerous, and I have one of field labourers in Dorsetshire and Somersetshire. But there is no notable difference in any of them. For example; the measurements of the ridge-interval gave the same results in the art-students and in the science-students, and I have prints of eminent thinkers and of eminent statesmen that can be matched by those of congenital idiots.[5] No indications of temperament, character, or ability are to be found in finger marks, so far as I have been able to discover. Of course these conclusions must not be applied to the general shape of the hand, which as yet I have not studied, but which seems to offer a very interesting field for exact inquiry. CHAPTER XIII GENERA The same familiar patterns recur in every large collection of finger prints, and the eye soon selects what appear to be typical forms; but are they truly "typical" or not? By a type I understand an ideal form around which the actual forms are grouped, very closely in its immediate neighbourhood, and becoming more rare with increasing rapidity at an increasing distance from it, just as is the case with shot marks to the right or left of a line drawn vertically through the bull's eye of a target. The analogy is exact; in both cases there is a well-defined point of departure; in both cases the departure of individual instances from that point is due to a multitude of independently variable causes. In short, both are realisations of the now well-known theoretical law of Frequency of Error. The problem then is this:--take some one of the well-marked patterns, such as it appears on a particular digit,--say a loop on the right thumb; find the average number of ridges that cross a specified portion of it; then this average value will determine an ideal centre from which individual departures may be measured; next, tabulate the frequency of the departures that attain to each of many successive specified distances from that ideal centre; then see whether their diminishing frequency as the distances increase, is or is not in accordance with the law of frequency of error. If it is, then the central form has the attributes of a true type, and such will be shown to be the case with the loops of either thumb. I shall only give the data and the