ociate with
agreeable ideas, as the whistling of birds, or purring of animals, that are
delighted; and some others, that we as generally associate with
disagreeable ideas, as the cries of animals in pain, the hiss of some of
them in anger, and the midnight howl of beasts of prey. Yet we receive no
terrible or sublime ideas from the lowing of a cow, or the braying of an
ass. Which evinces, that these emotions are owing to previous associations.
So if the rumbling of a carriage in the street be for a moment mistaken for
thunder, we receive a sublime sensation, which ceases as soon as we know it
is the noise of a coach and six.

There are other disagreeable sounds, that are said to set the teeth on
edge; which, as they have always been thought a necessary effect of certain
discordant notes, become a proper subject of our enquiry. Every one in his
childhood has repeatedly bit a part of the glass or earthen vessel, in
which his food has been given him, and has thence had a very disagreeable
sensation in the teeth, which sensation was designed by nature to prevent
us from exerting them on objects harder than themselves. The jarring sound
produced between the cup and the teeth is always attendant on this
disagreeable sensation: and ever after when such a sound is accidentally
produced by the conflict of two hard bodies, we feel by association of
ideas the concomitant disagreeable sensation in our teeth.

Others have in their infancy frequently held the corner of a silk
handkerchief in their mouth, or the end of the velvet cape of their coat,
whilst their companions in play have plucked it from them, and have given
another disagreeable sensation to their teeth, which has afterwards
recurred on touching those materials. And the sight of a knife drawn along
a china plate, though no sound is excited by it, and even the imagination
of such a knife and plate so scraped together, I know by repeated
experience will produce the same disagreeable sensation of the teeth.

These circumstances indisputably prove, that this sensation of the
tooth-edge is owing to associated ideas; as it is equally excitable by
sight, touch, hearing, or imagination.

In respect to the artificial proportions of sound excited by musical
instruments, those, who have early in life associated them with agreeable
ideas, and have nicely attended to distinguish them from each other, are
said to have a good ear, in that country where such proportions are in
fashio