BIOMETRY. 
By FRANCIS GALTON. 
This Journal is especially intended for those who ai'e interested in the 
application to biology of the modern methods of statistics. Those methods deal 
comprehensively with entire species, and with entire groups of influences, just as 
if they were single entities, and express the relations between them in an equally 
compendious manner. They commence by marshalling the values in order of 
magnitude from the smallest up to the largest, thereby converting a mob into 
•an orderly array, which like a regiment thenceforth becomes a tactical Tinit. 
Those to whom these considerations are new, will grasp the results more easily 
by thinking of the array in its simplest, though not necessarily in its most 
convenient, form for mathematical treatment. Let them conceive each value to 
be represented by an extremely slender rod of proportionate length, and the 
rods to be erected side by side, touching one another, upon a horizontal base. 
The array of closely packed rods will then form a plane area, bounded by 
straight lines at its sides and aiong its base, but by a flowing curve above, which 
takes note of every one of the values on which it is founded, however immense 
their multitude may be. The shape of the curve is characteristic of the particular 
group of values to which it refers, but all arrays have a family resemblance due to 
similarity of origin ; they all drop steeply at one end, rise steeply at the other, and 
have a sloping back. An array that has been drilled into some such formation as 
this, is the tactical unit of the new statistics. Its outline is expressed by a general 
formula whose constants are adapted to each particular case, and, being thus 
brought within the grip of mathematics, the internal relations of an array and 
their relations to those of any other ari-ay can be expressed in exact numerical 
forms. The new methods occupy an altogether higher plane than that in which 
ordinary statistics and simple averages move and have their being. Unfortunately 
the ideas of which they treat, and still more the many technical phrases employed 
in them, are as yet unfamiliar. The arithmetic they require is laborious, and the 
mathematical investigations on which the arithmetic rests are difficult reading even 
for experts ; moi-eover they are voluminous in amount and still growing in bulk. 
Consequently this new departure in science makes its appearance under conditions 
