galton.org 23
Sequence of Test Weights
23
under the most favourable circumstances, is barely four miles off, and
there is no sharpness of outline in the intervening waves. Besides this, the
life of a sailor is very unhealthy, as shown by his growing old
prematurely, and his eyes must be much tried by foul weather and salt
spray.
We inherit our language from barbarous ancestors, and it shows traces
of its origin in the imperfect ways by which grades of difference admit of
being expressed. Suppose a pedestrian is asked whether the knapsack on
his back feels heavy. He cannot find a reply in two words that cover more
varieties than (1) very heavy, (2) rather heavy, (3) moderate, (4) rather
light, (5) very light. I once took considerable pains in the attempt to draw
up verbal scales of more than five orders of magnitude, using those
expressions only that every cultivated person would understand in the
same sense; but I did not succeed. A series that satisfied one person was
not interpreted in the same sense by another.
The general intention of this chapter has been to show that a delicate
power of sense discrimination is an attribute of a high race, and that it has
not the drawback of being necessarily associated with nervous irritability.
SEQUENCE OF TEST WEIGHTS.
I will now describe an apparatus I have constructed to test the delicacy
with which weights may be discriminated by handling them. I do so
because the principle on which it is based may be adopted in apparatus for
testing other senses, and its description and the conditions of its use will
illustrate the desiderata and difficulties of all such investigations.
A series of test weights is a simple enough idea —the difficulty lies in
determining the particular sequence of weights that should be employed.
Mine form a geometric series, for the reason that when stimuli of all kinds
increase by geometric grades the sensations they give rise to will increase
by arithmetic grades, so long as the stimulus is neither so weak as to be
barely felt, nor so strong as to excite
