It is somewhat tedious to test many persons in succession, but any
one can test his own powers at odd and end times with ease and nicety,
if he happens to have ready access to suitable apparatus.

The use of tests, which, objectively speaking, run in a geometric
series, and subjectively in an arithmetic one, may be applied to
touch, by the use of wire-work of various degrees of fineness; to
taste, by stock bottles of solutions of salt, etc., of various
strengths; to smell, by bottles of attar of rose, etc., in various
degrees of dilution.

The tests show the sensitivity at the time they are made, and give
an approximate measure of the discrimination with which the operatee
habitually employs his senses. It does not measure his capacity for
discrimination, because the discriminative faculty admits of much
education, and the test results always show increased delicacy after
a little practice. However, the requirements of everyday life
educate all our faculties in some degree, and I have not found the
performances with test weights to improve much after a little
familiarity with their use. The weights have, as it were, to be
played with at first, then they must be tried carefully on three or
four separate occasions.

I did not at first find it at all an easy matter to make test
weights so alike as to differ in no other appreciable respect than
in their specific gravity, and if they differ and become known apart,
the knowledge so acquired will vitiate future judgments in various
indirect ways. Similarity in outward shape and touch was ensured by
the use of mechanically-made cartridge cases; dissimilarity through