The internal part of the ear is particularly formed for reflecting sounds, and may, in some measure, be compared to the cavern of a rock. In this cavity sounds are repeated, and by that means conveyed to the membranous part of the lamina, which being an expansion of the auditory nerves transmits them to the mind. The internal cavity of the ear, which is fashioned out in the temporal bone, like a cavern cut into a rock, seems to be fitted for the purposes of echoing sound with the greatest precision. One of the most common complaints in old age is deafness, which probably proceeds from the rigidity of the nerves in the labyrinth of the ear, augmenting as we advance in years, and when the membranous part of the lamina becomes ossified deafness is the consequence, and is in that case incurable. It sometimes happens from a stoppage of the wax, but it may then be relieved by art. In order to know whether the defect be an internal or art external one, let the deaf person put a repeating watch into his mouth, and if he hears it strike, he may be assured that his disorder proceeds from an external cause, and may be, in some measure, relieved. It often happens, that people with bad voices, and unmusical ears, hear better with one ear than the other, and suspecting there might be some analogy between the ears and eyes, as those who squint have more strength in one eye than the other, I made several experiments, and always found their defect in judging properly of sounds proceeded from the inequality of their ears, and their receiving by both at the same time unequal sensations, and those persons who hear false also sing false, without knowing it. They also frequently deceive themselves with regard to the side from whence the sound comes, generally supposing the noise to come on the part of the best ear. This, however, is only applicable to those who are born with a defect in the hearing. Such as are hard of hearing reap the same advantage from the trumpet made for this purpose that short-sighted persons do from concave glasses. As the sight is affected with age so is the hearing, and equally requires the assistance of art. Trumpets for assisting hearing might be easily enlarged, so as to increase sounds, in the same manner that the telescope does bodies; but they could be used to advantage only in places of solitude and stillness, as the neighbouring sounds would mix with the more distant ones, and the whole would produce in the ear nothing but tumult and confusion.