Personal identification and description / Francis Galton.

  • Francis Galton
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: Personal identification and description / Francis Galton. Source: Wellcome Collection.

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    Then the ratio borne by the uncertain entries to the whole number of entries is as c,c, + e,e,to A B. This, as seen by the diagram, is a very large proportion. There is a dilemma from which those who adopt hard-and-fast lines of classification cannot escape: either the fringe of uncertainty must be dangerously wide, or else the delicacy with which measures are made cannot be turned to anything like its full account. If the delicacy is small, the fringe of uncertainty must be very wide; if the delicacy is great, the summed widths of all the fringes will be narrow, so long as there are only a few classes; but, on the other hand, by having only afew classes, most of the advantages of possessing delicate observations are wasted. ‘The bodily measure- ments are so dependent on one another that we cannot afford to neglect small distinctions in an attempt to make an effective classi- fication. Thus long feet and long middle-fingers usually go together. We therefore want to know whether the long feet in some particular person are accompanied by very long, or moderately long, or barely long fingers, though the fingers may in all three cases have been treated as long in M. Bertillon’s system of classes, because they would be long as compared with those of the general population. Certainly his eighty-one combinations are far from being equally probable. The more numerous the measures the greater would be their interdepend- ence, and the more unequal would be the distribution of cases among the various possible combinations of large, small, and medium values. No attempt has yet been made to estimate the degree of their inter- dependence. I am therefore having the above measurements (with slight necessary variation) recorded at my anthropometric laboratory for the purpose of doing so. This laboratory, I may add, is now open to public use under reasonable restrictions. It is entered from the Science Collections in the Western Galleries at South Kensington. Mechanical Selector.—Feeling the advantage of possessing a method of classification that did not proceed upon hard and fast lines, I con- trived an apparatus that is quite independent of them, and which I call a mechanical selector. Its object is to find which set, out of a standard collection of many sets of measures, resembles any one given set within any given degree of unlikeness. No one measure in any of the sets selected by the instrument can differ from the corresponding measure in the given set by more than a specified value. The apparatus is very simple; it applies to sets of measures of every description, and ought to act on a large scale as well as it does on a small one, with great rapidity, and be able to test several hundred sets by each movement. It relieves the eye and brain from the intolerable strain of tediously comparing a set of many measures with each of a large number of successive sets, in doing which a mental allowance has to be made for a plus or minus deviation of a specified amount in every entry. It is not my business to look after prisoners, and I do not fully know what need may really exist for new methods of quickly identifying suspected persons. If there be any real need, I should
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