humanfaculty4 - page 48 of 305

Inquiries into Human Faculty

of them may be disposed too much towards the ends, as in a dumb-bell, or

gathered too much towards the centre. The period of oscillation will differ

widely in the two cases, as may be shown by suspending the cartridges by

strings round their middle so that they shall hang horizontally, and then by

a slight tap making them spin to and fro round the string as an axis.

The touch is very keen in distinguishing all these peculiarities. I have

mentioned them, and might have added more, to show that experiments on

sensitivity have to be made in the midst of pitfalls warily to be avoided.

Our apparently simplest perceptions are very complex. We hardly ever act

on the information given by only one element of one sense, and our

sensitivity in any desired direction cannot be rightly determined except by

carefully-devised apparatus judiciously used.

I contrived a small whistle for conveniently ascertaining the upper

limits of audible sound in different persons, which Dr. Wollaston had

shown to vary considerably. He used small pipes, and found much

difficulty in making them. I made a very small whistle from a brass tube

whose internal diameter was less than one-tenth of an inch in diameter. A

plug was fitted into the lower end of the tube, which could be pulled out

or pushed in as much as desired, thereby causing the length of the bore of

the whistle to be varied at will. When the bore is long the note is low;

when short, it is high. The plug was graduated, so that the precise note

produced by the whistle could be determined by reading off the

graduations and referring to a table. (See Appendix.)

On testing different persons, I found there was a remarkable falling off

in the power of hearing high notes as age advanced. The persons

themselves were quite unconscious of their deficiency so long as their

sense of hearing low notes remained unimpaired. It is an only too amusing

experiment to test a party of persons of various ages, including some

rather elderly and self-satisfied personages. They are indignant at being

thought deficient in the power of hearing, yet