-^ g Ohfervatms yef[iecllng Acoujiu Injirlimtnts. 



bodies do not vibrate during the propagation of found, becaufe the w.Uer in his curioos 

 experiment of the watch was not fcen to move. He has overlooked the very great num. 

 ber and minutenefs of the vibrations required to produce found. They cannot be vlfible 

 but in cafes of extreme fimplicity and intenfity. The firing o£ a muf.cal inftrument emits 

 found Ion- after itG vibrations have ceafed to be vifible. He likewife, at the end of his 

 fecond part, objeas to the theory of Mnupertuis, which fuppofes that fonorous and refonart 

 bodies fubdlvide themfelves fo as to vibrate differently in different parts. But the body m 

 queftion may be confidered under different points of view. l. As the medium of found, it 

 may condua or tranfmit every found indifferently. 2. If its Hmplicity of figure and tex- 

 ture be fucl> as to produce very few founds at a time, it will, upon the whole, emit a muf.- 

 cal tone. For I confider a mufical tone as one or more fimple founds in concord with each 

 other ; and a noife, as a greater number not poffeff.ng the fame relation. Thus, the noifc 

 produced by prefTuig down an indifcriminate number of contiguous keys in the organ, is fo 

 far from being muGcal, that it feems aftonilhing that the aggregate of pipes fo melodious 

 fliould produce a found fo harfh. 3. Or the body in queftion may affill or impede the 

 found of another fimple body, fuch as a ftring with which it is in contaft. When it affift:^ 

 that found, it does not feem improbable that the effea pointed out by Maupertu.s may really 

 take place For the divifion of bodies, his fuppofition requires, is known to take place m 

 the finsle ftring which gives the trumpet notes, and has on that account been called the 

 trumpet marine ; and alfo in bells, which not only give a fet of diftina contemporaneous 

 tones differing in acutenefs, but to a certain extent are found to alter the fyftem according 

 to the plan of percuffion. And again, it will readily be imagined by thofe who take fo 

 much pains in experiments for fixing the found poft of the violin, that the refonance which 

 is fo much affeaed by this difpofition, is more probably of the whole inftrument than merely 

 cf its parts as conduaors of found. 



T The figure of the external ear, which is made up of a ferles of concavities with ftops 

 or bridges interpofed, is an objea which, as far as I know, has never yet been explained 

 or enquired into. In the cat and other animals this ftruaure appears to be very compli- 

 cated After the found or aerial undulation has been modified and conveyed into the ear 

 through this apparatus, k is received upon the ftretched membrane called the tympanum. 

 This as well as the other membranous parts of the internal ear, fecms evidently adapted 

 to vibrate by the aaion of found ; and moft probably after the manner that a mufical ftri-ig 

 vibrates when another ftring is made to found in its vicinity, and emits a tone in concord 

 not too remote from unifon. From this fafl and the formation of the ear, a queftion may 

 be propofed of fome confequence with regard to the conftruaion'of acouftic inftruments : 

 Whether the found produced by a remote body or that which is emitted by a correfpondent 

 vibrating body, at alefs diftance from the organ, be the moft perceptible? For example, if 

 tvo ftrings, A and B, be tuned in unifon, and the ftring A be ten feet from the ear, while the 

 ftring B is placed at the diftance, for example, of one indi from tlie fame organ i-whether 

 the fecondary found of B, when A is ftruck, may not be more perceptible than the original 

 found of A ? It is unneceffary to enter into confiderations of the mechanical circumftanccs 

 under which, from theory, this or the contrary effeft may take place. It may be fuff.c.e^t 

 in this very remote view of the fubjeil to remark, that in point of faa the influence of 

 founds may extend further than the organ can perceive them. I was once in a room facing 



the 



