CHAP. III.

PART I, ception; a perception, a sensation, or a sensation its object, than that an exertion should resemble an Of Touch. arm; an arm, a lever; or a lever, a weight; nor is it less absurd to make the want of resemblance between the cause, the means, and the end, a ground for doubting the reality of either, in the one case, than in the other. I could therefore wish to drop or modify the use of the word idea; but it has become too general and established for an individual to attempt it; and I have only to intreat the reader to keep these distinctions in his mind, and apply them occasionally.

12. Among the pleasures of sense, more particularly among those belonging to touch, there is a certain class, which, though arising from negative causes, are nevertheless real and positive pleasures: as when we gradually sink from any violent or excessive degree of action or irritation into a state of tranquillity and repose : I say gradually; for if the transition be sudden and abrupt, it will not be pleasant; the pleasure arising from the inverted action of the nerves, and not from the utter cessation of action.

13. From this inverted action arises the gratification which we receive from a cool breeze, when the body has been excessively

CHAP. III.

heated; or from the rocking of a cradle, PART I or the gentle motion of a boat, or easy carriage, after having been fatigued with violent Of Touch. exercise. Such, too, is that which twilight, or the gloomy shade of a thicket, affords to the eye, after it has been dazzled with the blaze of the mid-day sun; and such, likewise, is that, which the ear receives, from the gradual diminution of loudness of tone in music; and it is by alternately ascending and descending this scale, that what is called (by a metaphor taken from painting) the chromatic in that art, is produced: but why the sensation caused by the ascent of the scale should be called pleasure, and that caused by its descent, delight, as distinguished by an eminent writer*, I cannot discover.

*Sublime and Beautiful, P. I. s, iv,

PART I.

CHAP. IV.

Of Hearing.

CHAPTER IV.

OF HEARING.

1. SOUND is produced by the vibrations of elastic air or some other fluid contained in it, and communicated to the interior of organs perception by means of the drum of the ear and auditory nerves; which are formed by nature with a peculiar kind of irritability suited to such 'vibrations, which have no effect on any other part of the body, how exquisite soever its sensibility may be. They have, nevertheless, a very strong and marked effect upon the hardest substances in nature, provided they are such as are capable of receiving vibrations in unison: whence sound will break a glass, at the same time, that it cannot move a feather or the flame of a candle; nor make any perceptible impression upon the ball of the eye.

2. Its vibrations, indeed, seem to be communicable to every hard and elastic substance; as appears from the ticking of a watch, or any other minute sound being conveyed to almost any distance by a pole or wire sonorous object to the ear.

extending from the Where the drum of

that organ, too, is diseased; and the sense of PART I. hearing consequently. lost or impaired, the low

CHAP. IV.

est whisper will, nevertheless, be distinctly of Hearing. heard, if spoken to one end of a bar of metal or glass, while the other is held between the teeth of the person addressed: but if the disease extends to the auditory nerves; so as to deprive them of their irritability, nothing can be heard. by these or any other means. The sound, therefore, appears, in this instance, to be conveyed to those nerves, which communicate with the brain, by means of vibrations received by one solid and elastic substance from another; and thus continued through the bar, the teeth, and the jaw bones.

3. Many of these solid bodies, which are so susceptible of the vibrations of sound, such as glass, and different kinds of metal, are impenetrable to air: wherefore I suspect that sound is produced by some finer fluid mixed with air; and pervading elastic, as light does transparent bodies. Of this fluid, however, if such there be, we can never obtain any adequate knowledge: for, as it is only perceived, as the vehicle of impressions to one sense, our ideas of it must always remain in nearly the same state as those which a man born blind can form of the light of the sun by feeling its warmth. That hard

CHAP. IV.

Of Hearing.

PART I. and solid substances should transmit this light, which is excluded by the most soft and porous, is equally unaccountable, as that they should transmit sound. In both, probably, there is a peculiar distribution of the component particles, respectively adapted to the admission of a particular fluid, and of that only.

4. But whatever be the nature of the substance, which produces sound, the sensations, caused by its vibrations upon the organs of hearing, will depend upon the same principles, as those produced by other substances on other organs. Certain modes and degrees of irritation will be pleasant, others painful, and others insipid; and these will vary in different individuals. according to the different degrees of sensibility in their respective organs. In some sorts of dogs, this sensibility is so exquisite, that the sound of a fife or other very shrill instrument, though perfectly in harmony, gives them very acute pain, when near to their ears; as they testify by loud howlings and complainings. The filing of a saw, or other harsh and discordant sound of that kind, though not loud, will create a very uneasy and even painful sensation in the human organs, which we commonly call setting the teeth on edge; and it seems to be produced by extend-" ing the vibrations from the ears to the teeth, in