David Hartley

“ Thus it is not uncommon for a person to receive a series of sensations, carry on a train of thought, and perform a course of external actions, which have little connexion with each other, at the same time. Now to this we may answer, that vibrations as different from each other do, in fact, exist together in common air, in such a manner as to be perceived distinctly. ”

“ The ideas which audible impressions leave in the region of the brain, that corresponds to the auditory nerves, are, next to the ideas of sight, the most vivid and definite of any; and all the observations above made upon the ideas of sight may be applied to those of hearing, proper changes and allowances being made. ”

“ And thus each letter may be distinguished from every other by hearing.
Thirdly, It is agreeable to all this, that it is difficult at great distances to distinguish the tone of one musical instrument from another, or of any from the tone of a human voice, cæteris paribus; or to distinguish articulate sounds from one another. For at great distances the vibrations of the air are circular to sense, and all the ascents, descents, eruptions and interruptions of sound, which distinguish one compound sound from another, are confounded by numberless reflections from the intermediate bodies. ”

“ Thus, after hearing music, conversing much with the same person, in general disorders of the brain, or particular ones of the nervous spasmodic kind in the stomach, after taking opium, in dreams, in madness, trains of audible ideas force themselves upon the fancy, in nearly the same manner, as trains of visible ideas do in like cases. ”

“ As there is an artificial memory relative to the eye, by which trains of visible ideas, laid up in the memory in a certain order, are made to suggest both things themselves, and the order in which we desire to remember them ”

“ An accurate inquiry into the mental progress of persons deprived of the advantages of language, by being born deaf, would be a still better test of the theory of these papers, than a like inquiry concerning persons born blind. ”

“ They may perhaps, as was above conjectured of the radiated fibres of the iris, depend chiefly on the influences which descend from the brain, and therefore act always, when the other two will give them leave. It is most probable, that the four muscles act in various proportions and combinations, so as to answer a variety of purposes. But there is very little, that is satisfactory, to be met with in books of anatomy and physiology hitherto, concerning the peculiar minute uses and functions of the several parts of the organ of hearing. ”

“ LXIX.—To explain in what Manner, and to what Degree, agreeable and disagreeable Sounds contribute, in the way of Association, to the Formation of our intellectual Pleasures and Pains.
As all moderate and tolerably uniform sounds please young children, and the original pleasures from concords sounded together, from the succession of both concords and discords, and even from clear musical sounds, considered separately, remain with us through the whole progress of life, it is evident, that many of our intellectual pleasures must be illuminated and augmented by them. ”

“ Now, as the vibrating of the membrana tympani are synchronous to those of the air, they may either excite synchronous ones in the particles of the auditory nerves, and thus be distinguished from each other in respect of frequency by the mind; or if every pulse of the air, and oscillation of the membrana tympani, excite innumerable infinitesimal vibrations in the auditory nerves, the renewal of these at different intervals according to the different gravity or acuteness of the sound will, however, afford a like criterion. ”

“ We seem also to have a voluntary power of preparing the ear previously for very strong, or very weak sounds, which we expect to hear, just as it was before observed of the eye, that we can suit it previously to see at an expected distance. ”

“ And the general tendency which is found in natural bodies, either to yield a sound upon percussion, or at least to support and convey sounds by receiving isochronous vibrations, and reflecting them, shews, that there are latent active powers in the small parts of bodies, which dispose them to vibrate. ”

“ By this means we are much better qualified to receive information, with mental pleasure and improvement, from them; and the ear becomes, like the eye, a method of perception suited to the wants of a spiritual being. ”

“ Fourthly, We may observe, that as the preserving the distinction of place is the chief end of the coats and humours in the organ of sight, so the distinction of time is of the greatest importance in hearing. It seems probable therefore, that the membrana tympani, small bones, and their muscles, are so contrived, as by their actions to preserve the distinction of time, i.e. to extinguish strong sounds, and to keep up weak ones, so as that the last may not be too much overpowered by the continuance of the first ”

“ For the theory of sounds deduced from the nature of an elastic fluid, and the tremors of the particles of sounding bodies, and afterwards verified, as it has been, by numerous experiments, becomes a guide to us in all inquiries into the vibrations of other elastic mediums, such as the æther, and into the effects, which such vibrations must impart to and receive from the small particles that are surrounded by the elastic medium. ”

“ Since grave sounds are in general loud, acute ones weak, the relaxation of the membrana tympani, which first attends upon loud sounds automatically, will afterwards, by association, be made to attend upon grave ones, even though they are not loud; and, in like manner, the membrane will be tense, from acute sounds, though they should be strong ”

“ It seems to agree with this, that some partially deaf persons can hear best, when driven in a coach over stones or gravel; i.e. when all the parts of their bodies, and particularly those of the bones, are put into a vibrating motion. ”

“ It is to be observed farther, that there is a difficulty in performing both the things here mentioned; that confusion does often arise; and that where any person is remarkable for doing more than one thing at once, it is in consequence of great practice, and also of exquisite mental powers, i.e. ”