or any other fractional grade in the other. This, it will be remarked,
is a very simple method of comparison, absolutely independent of any
theory, and applicable to any statistical groups whatever, whether of
physical or of mental qualities. Wherever we can sort in order,
there we can apply this method. Thus, in the above examples, suppose
A and B had been selected because they were equal when compared
together, then we can concisely express the relative merits of the
two classes to which they respectively belong, by saying that 16°.6
in the one is equal to 50° (the median) in the other.

I frequently make statistical records of form and feature, in the
streets or in company, without exciting attention, by means of a
fine pricker and a piece of paper. The pricker is a converted silver
pencil-case, with the usual sliding piece; it is a very small one,
and is attached to my watch chain. The pencil part has been taken
out and replaced by a fine short needle, the open mouth of the case
is covered with a hemispherical cap having a hole in the centre, and
the adjustments are such that when the slide is pushed forward as
far as it can go, the needle projects no more than one-tenth of an
inch. If I then press it upon a piece of paper, held against the
ball of my thumb, the paper is indelibly perforated with a fine hole,
and the thumb is not wounded. The perforations will not be found to
run into one another unless they are very numerous, and if they
happen to do so now and then, it is of little consequence in a
statistical inquiry. The holes are easily counted at leisure, by
holding the paper against the light, and any scrap of paper will
serve the purpose. It will be found that the majority of inquiries
take the form of "more," "equal to," or "less," so I arrange the
paper in a way to present three distinct compartments to the pricker,
and to permit of its being held in the correct position and used by