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30   ENGLISH MEN OF SCIENCE.   [carer.

separate qualities are treated in the table. As regards height, there is a stricter method of investigation, which statisticians will appreciate. It is well known, by repeated experience, that the heights of men and of women in any large group are distributed according to the " law of frequency of error." In other words, the proportionate number of people of different heights corresponds to what would have been the case supposing stature to be due to the aggregate action of many small and independent variable causes. The probability is inconceivably small that all the independent causes should. in any given case co-operate to produce an excess of height; if they did so, the result would be a Brobdignagian giant ; or that they should all co-operate to produce a deficiency in height, in which case the result would be a Lilliputian dwarf. On the other hand, the probability is great that the number and effects of the causes in excess and those in deficiency of their several

average values will be pretty equal. As for these

and all other intermediate cases, their relative

frequency is determined by the above law, which