Imágenes de páginas

Many experiments are mentioned by Kircher manner, nearly fill these semicircular canals. A and others on the communication of sound third department of the nerve is spread over the through solid bodies, such as masts, yards, and external surface of another membranaceous bag, other long beams of dry fir, with similar results. which lies between the one just now mentioned Dr. Monro has published a particular account of and the cochlea, but, having no communication very curious experiments on the propagation of with either, almost completely filling the resound 'through water, in his Dissertation on the mainder of the vestibule. Thus the vestibule Physiology of Fishes ; so that it now appears and canals seem only a case for protecting this that air is by no means the only vehicle of sound. sensitive membranaceous vessel, which is almost In 1760 Cotunni published his important disco- but not altogether in contact with the osseous very that the labyrinth or inmost cavity of case, being separated by a delicate and almost the ear in animals is completely filled 'with fluid cellular substance. The fibrillous expanwater. This, after some contest, has been com sion of the nerve is not indiscriminately diffused pletely demonstrated (see Meckle Junior de over the surface of these sacculi, but evidently Labyrinthi Auris Contentis, Argentor, 1777), directed to certain foci, where the fibres are conand it seems now to be admitted by all. This stipated. And this is the last appearance of the being the case, our notions of the immediate fibrous state of the nerve; for, when the inside cause of sound must undergo a great revolution, of these sacculi is inspected, no fibres appear, and a new research must be made into the way but a pulp (judged to be nervous from its siin which the nerve is affected; for it is not milarity to other pulpy productions of the brain) enough that we substitute the undulations of wa- adhering to the membranaceous coat, and not ter for those of air in the labyrinth. The well separable from it by gently washing it. It is informed mechanician will see at once, that the more abundant, that is of greater thickness, opvivacity of the agitations of the nerve will be posite to the external fibrous foci. No organical greatly increased by this substitution; for if wa structure could be discovered in this pulp, but ter be perfectly elastic, through the whole extent it probably is organised; for, besides this adherof the undulatory agitation which it receives, its ing pulp, the water in the sacculi was observed effect will be greater in proportion to its specific to be clammy or mucous; so that in all probagravity: and this is confirmed by an experiment bility the vascular or fibrous state of the nerve is very easily made. Immerse a table bell in water succeeded by an uninterrupted production (percontained in a large thin glass vessel. Strike it haps columnar like basalt, though not cohering); with a hammer. The sound will be heard as if and this at last ends in simple dissemination, the bell had been immediately struck on the symmetrical, however, where water and nerve sides of the vessel. The filling of the labyrinth are alternate in every direction. To these obof the ear with water is therefore an additional servations of Scarpa, Comparetti adds the curimark of the wisdom of the Great Artist. But ous circumstances of another and regular tymthis is not enough for informing us concerning panum in the foramen rotundum, the cylindric the ultimate mechanical event in the process of cavity of which is enclosed at both ends by a hearing. The manner in which the nerve is ex fine membrane. The membrane which separates posed to these undulations must be totally dif- it from the cochlea appears to be in a state of ferent from what was formerly imagined. The variable tension, being drawn up to an umbo by filaments and membranes which have been de a cartilaginous speck in its middle, which he scribed by former anatomists must have been thinks adheres to the lamina spiralis, and thus found by them in a state quite unlike to their serves to strain the drumhead as the malleus situation and condition in the living animal. Ac- strains the great membrane known to all. These cordingly the most eminent anatomists of Europe are most important observations, and must greatseem at present in great uncertainty as to the ly excite the curiosity of a truly philosophical state of the nerve, and are keenly occupied in mind, and deserve the most careful enquiry into observations to this purpose. The descriptions their justness. If these are accurate descriptions given by Monro, Scarpa, Camper, Comparetti, of the organ, they seem to conduct us farther and others, are full of most curious discoveries, into the secrets of nature than any thing yet which make almost a total change in our notions known. They promise to give us the greatest of this subject, and will, we hope, be produc- step yet made in physiology, viz. to show us the tive of most valuable information. Scarpa has last mechanical fact which occurs in the long discovered that the solid cavity called the laby- train interposed between the external body and rinth, contains a threefold expansion of the au the incitement of our sensitive system.

But ditory nerve. One part of it, the cochlea, there are, as yet, great and essential differences contains it in a fibrillous state, ramified in a in the description given by those celebrated namost symmetrical manner through the whole of turalists. There seems to be no abatement of the zona molis of the lamina spiralis, where it ardor in the researches of the physiologists; and anastomoses with another production of it dif- they will not remain long ignorant of the truth fused over the general lining of that cavity. or mistake in the accounts given by Scarpa and Another department of the nerve, also in a fibrous Comparetti. state, is spread over the external surface of a To illustrate the cause of sound, it may be membranaceous bag, which nearly fills that part observed, 1st, That a motion is necessary in of the vestibule into which the semicircular ca- the sonorous body for the production of sound. nals open, and also that orifice which receives 2dly, That this motion exists first in the small the impressions of the stapes. This bag sends and insensible parts of the sonorous bodies, and off tubular membranaceous ducts, which, in like is excited in them by the mutual collision agairist

each other, which produces the tremulous mo or more than 7520, is distinguishable by the tion so observable in bodies that have a clear human ear. According to this doctrine, the limit sound, as bells, musical chords, &c. 3dly, That of our hearing, as to acute and grave, is an idthis motion is communicated to, or produces a terval of eight octaves.—Tentam. Nov. Theor. like motion in the air, or such parts of it as are Mus. cap. 1. sect. 13. fit to receive and propagate it. Lastly, That this The velocity of sound is the same with that of motion must be communicated to those parts the aërial waves, and does not vary much, whe that are the proper and immediate instruments ther it go with the wind or against it. By the of hearing. Now that motion of a sonorous body wind indeed a certain quantity of air is carried which is the immediate cause of sound may be from one place to another; and the sound is acowing to two different causes; either the percus- celerated while its waves move through that part sion between it and other hard bodies, as in of the air, if their direction be the same as ibat drums, bells, chords, &c.; or the beating and of the wind. But, as sound moves vastly swifter dashing of the sonorous body and the air imme- than the wind, the acceleration it will hereby rediately against each other, as in flutes, trumpets, ceive is but inconsiderable; and the chief effect &c. But in both these cases the motion, which we can perceive from the wind is that it isis the consequence of the mutual action, as well creases and diminishes the space of the wares, as the immediate cause of the sonorous motion so that by the help of it the sound may be heard which the air conveys to the ear, is supposed to to a greater distance than otherwise it would. be an invisible, tremulous, or undulating motion That the air is the usual medium of sound apin the small and insensible parts of the body. pears from various experiments in rarefied and Perrault adds that the visible motion of the condensed air. In an unexhausted receiver a grosser parts contributes no otherwise to sound small bell may be heard to some distance; bat than as it causes the invisible motion of the when exhausted it can scarcely be heard at the smaller parts, which he calls particles, to distin- smallest distance. When the air is condeosed, guish them from the sensible ones, which he calls the sound is louder in proportion to the condenparts, and from the smallest of all, which are sation, or quantity of air crowded in; of which called corpuscles.

there are many instances in Hauksbee's experiThe sonorous body having made its impres- ments, ip Dr. Priestley's, and others. Besides, sion on the contiguous air, that impression is sounding bodies communicate tremors to distant propagated from one particle to another, accord- bodies; for example, the vibrating motion of a ing to the laws of pneumatics. A few particles, musical string puts others in motion, wliose teofor instance, driven from the surface of the body, sion and quantity of matter dispose their vibrapush or press their adjacent particles into a less tions to keep time with the pulses of air propaspace; and the medium, as it is thus rarefied in gated from the string that was struck. Galileo one place, becomes condensed in the other ; but explains this phenomenon by observing that a the air thus compressed in the second place is, heavy pendulum may be put in motion by the by its elasticity, returned back again, both to its least breath of the mouth, provided the blasts be former place and its former state; and the air often repeated, and keep time exactly with the contiguous to that is compressed; and the like vibrations of the pendulum; and also by the like obtains when the air less compressed, expanding art in raising a large bell. itself, a new compression is generated. 'There It is not air alone that is capable of the itfore from each agitation of the air there arises a pressions of sound, but water also; as is manimotion in it analogous to the motion of a wave fest by striking a bell under water, the sound of on the surface of the water; which is called a which may plainly enough be heard, only not so wave or undulation of air. In each wave the loud, and also a fourth deeper, according to goou particles go and return back again through very judges in musical notes. And Mersenne says, a short equal spaces; the motion of each particle sound made under water is of the same tone or being analogous to the motion of a vibrating note as if made in air and heard under the pendulum while it performs two oscillations; water. and most of the laws of the pendulum, with very The velocity of sound, or the space through little alteration, being applicable to the former. which it is propagated in a given time, has been

Sounds are as various as are the means that very differently estimated by authors who have concur in producing them. The chief varieties written concerning this subject. Roberval states result from the figure, constitution, quantity, &c., it at the rate of 560 feet in a second; Gassendus of the sonorous body; the manner of percussion, at 1473; Mersenne at 1474; Duhamel, in the with the velocity, &c., of the consequent vibra- History of the Academy of Sciences at Paris, at tion; the state and constitution of the medium; 1338; Newton at 968; Derham, in whose meathe disposition, distance, &c., of the organ; the sure Flamsteed and Halley acquiesce, at 1142. obstacles between the organ and the sonorous The reason of this variety is ascribed by Derham object and the adjacent bodies. The most not- partly to some of those gentlemen using strings able distinction of sounds, arising from the vari- and plummets instead of regular pendulums; ons degrees and combinations of the conditions and partly to the too small distance between the above-mentioned, are into loud and low (or sonorous body and the place of observation; and strong and weak); into grave and acute (or sharp partly to no regard being had to the winds. But and flat, or high and low); and into long and by the accounts since published by M. Cassini short. The management of which is the office de Thury, in the Memoirs of the Royal Acaof music. Euler is of opinion that no sound demy of Sciences at Paris, 1738, where cannon making fewer vibrations than thirty in a second, were fired at various as well as great distances,

under many varieties of weather, wind, and other whole height above each other as in the ancient circumstances, and where the measures of the theatres. Paint has generally been thought undifferent places had been settled with the utmost favorable to sound, from its being so to musical exactness, it was found that sound was propa- instruments, whose effects it quite destroys. Mugated, on a medium, at the rate of 1038 French sical instruments mostly depend on the vibrative feet in a second of time. But the French foot is or tremulous property of the material, which a in proportion to the English as fifteen to sixteen; body of color hardened in oil must very much and consequently 1038 French feet are equal to alter; but we should distinguish that this regards 1107 English feet. Therefore the difference of the formation of sound, which may not altogether the measures of Derham and Cassini is thirty- be the case in the progress of it. five English feet, or thirty-three French feet, in Water has been little noticed with respect to a second. The medium velocity of sound there- its conducting sound; but it will be found to be fore is nearly at the rate of a mile, or 5280 feet, of the greatest consequence. 'I had often,' says in four seconds and two-thirds, or a league in our author, perceived in newly-finished houses fourteen seconds, or thirteen miles in a minute. that, while they were yet damp, they produced But sea miles are to land nearly as seven to six ; echoes; but that the echoing abated as they and therefore sound moves over a sea mile in dried. When I made the following experiment five seconds and one-third nearly, or a sea league there was a gentle wind; consequently the water in sixteen seconds. Farther, it is a common was proportionally agitated. I chose a quiet observation, that persons in good health have part of the river Thames, near Chelsea Hospital, about seventy-five pulsations, or beats of the and with two boats tried the distance the voice artery at the wrist, in a minute; consequently would reach. On the water we could distinctly in seventy-five pulsations sound lies about thir- hear a person read at the distance of 140 feet, teen land miles, or eleven sea miles and one on land at that of seventy-six. It should be ob. seventh, which is about one land mile in six served that on land no noise intervened; but on pulses, or one sea mile in seven pulses, or a the river some noise was occasioned by the flow. league in twenty pulses. Hence the distance of ing of the water against the boats: so that the objects may be found by knowing the time em- difference on land and on water must be much ployed by sound in moving from those objects more.' to an observer. For example, on seeing the

• Watermen observe that when the water is flash of a gun at sea, if fifty-four beats of the still, and the weather quite calm, if no noise inpulse at the wrist were counted before the report tervene, a whisper may be heard across the river; was heard ; the distance of the gun will easily and that with the current it will be carried to a be found by dividing fifty-four by twenty, which much greater distance, and vice versâ against the gives 2:7 leagues, or about eight miles.

current Mariners well know the difference of In an ingenious treatise, published 1790, by sound on sea and land. Mr. G. Saunders, on theatres, he relates many “When a canal of water was laid under the pit experiments made by himself on the nature and Avor of the theatre of Argentino, at Rome, a surpropagation of sound; and shows the great effect prising difference was observed; the voice has of water, and some other bodies, in conducting since been heard at the end very distinctly, where of sound, probably by rendering the air more it was before scarcely distinguishable. It is obdense near them. Some of his conclusions and servable that, in this part, the canal is covered observations are as follow :— Earth may be sup- with a brick arch, over which there is a quantity posed to have a twofold property with respect to of earth, and the timber floor over all. The villa sound. Being very porous it absorbs sound, Simonetta near Milan, so remarkable for its which is counteracted by its property of con- echoes, is entirely over arcades of water. Anducting sound, and occasions it to pass on a other villa near Rouen, remarkable for its echo, plane, in an equal proportion to its progress in is built over subterraneous cavities of water. A air, unencumbered by any body. If a sound be reservoir of water domed over, near Stanmore, sufficiently intense to impress the earth in its has a strong echo. tremulous quality, it will be carried to a consi "I do not remember ever being under the derable distance, as when the earth is struck arches of a stone bridge that did not echo; which with any thing hard, as by the motion of a car- is not always the case with similar structures on riage, horses' feet, &c. Plaster is proportionally land. A house in Lambeth Marsh, inhabited by better than loose earth for conducting sound as Mr. Turtle, is very damp during winter, when it it is more compact. Clothes of every kind, par- yields an echo which abates as the house becomes ticularly woollen cloths, are very prejudicial to dry in summer.' Kircher observes that echoes sound : their absorption of sound may be com- repeat more by night than during the day; he pared to that of water, which they greedily im- makes the difference to be double. Dr. Plott bibe.

says the echo in Woodstock park repeated sevenA number of people seated before others, as teen times by day, and twenty by night. And in the pit or gallery of a theatre, do considerably Addison's experiment at the villa Simonetta was prevent the voice reaching those behind; and in a fog, when it produced fifty-six repetitions. hence it is that we hear so much better in the • After all these instances I think little doubt front of the galleries, or of any situation, than can remain of the influence water has on sound; behind others, though we may be nearer to the and I conclude that it conducts sound more than speaker. Our seats, rising so little above each any other body whatever. After water, stone other, occasion this defect, which would be re- may be reckoned the best conductor of sound. medied could we have the seats to rise their To what cause it may be attributed I leave to

future enquiries : I have confined myself to speak pends on the disposition and state of the sonoof facts only as they appear. Stone is sonorous, rous body, or the circumstances of the place; but gives a harsh disagreeable tone, unfavorable but the ideas of the differences must be sought to music.

from observation. · Brick, in respect to sound, has nearly the Smooth and rough sounds depend principally same properties as stone. Part of the garden on the sounding body; of these we have a potwall of the late W. Pitt, esq., of Kingston in able instance in strings that are uneven, and not Dorsetshire, conveys a whisper to the distance of the same dimension or constitution throughof nearly 200 feet.

out. Perrault, to account for roughness and «Wood is sonorous, conductive, and vibrative; smoothness, maintains, there is no such thing as of all materials it produces a tone the most agree a simple sound; but that the sound of the same able and melodious; and it is therefore the fittest chord or bell is a compound of the sounds of for musical instruments, and for lining of rooms the several parts of it; so that where the parts and theatres. The common notion that whis are homogeneous, and the dimensions or figure pering at one end of a long piece of timber would uniform, there is always such a perfect mixture be heard at the other end, I found by experiment and union of all the sounds as makes one unito be erroneous.

A stick of timber sixty-five feet form and smooth sound: contrary conditions long being slightly struck at one end, a sound produce harshness. In effect, a' likeness of was heard at the other, and the tremor very per- parts and figure make a uniformity of vibraceptible: which is easily accounted for when we tions, by which a great number of similar and consider the number or length of the fibres that coincident motions conspire to fortify and imcompose it, each of which may be compared to prove each other, and unite, for the more effeca string of catcut.'

tual producing of the same effect. This account Sounds are distinguished, with regard to he confirms from the phenomenon of a bell music, into simple and compound, and that two which differs in tone according to the part it is ways. In the first, a sound is said to be com struck in ; and yet, strike it any where, there is a pound, when a number of successive vibrations motion over all the parts. Hence he considers of the sonorous body, and the air, come so fast the bells as composed of an infinite number of upon the ear that we judge them the same con rings, which, according to their different dimentinued sound; as in the phenomenon of the sions, have different tones, as chords or strings circle of fire, caused by putting the fire-end of of different lengths have; and, when struck, the a stick in a quick circular motion; where, sup- vibrations of the parts immediately struck spea posing the end of the stick in any point of the cify the tone, being supported by a sufficient circle, the idea we receive of it there continues number of consonant tones in other parts. This till the impression is renewed by a sudden re must be allowed, that every note of a stringed

A simple sound, with regard to this com instrument is the effect of several simple sounds; position, should be the effect of a single vibra- for there is not only the sound resulting from tion, or of so many vibrations as are necessary the motion of the string, but that from the moto raise in us the idea of sound. In the second tion of the parts of the instrument, which has a sense of composition, a simple sound is the pro- considerable effect in the total sound, as is eviduct of one voice, or one instrument, &c. A dent from hence that the same string on different compound sound consists of the sounds of seve

violins sounds very differently. ral distinct voices or instruments, all united in But Perrault affirms the same of every string the same individual time and measure of dura- without considering the instrument. Every part tion, that is, all striking the ear together, what- of the string, he says, has its particular vibraever their other differences may be. But in tions, different from the gross and sensible vibrathis sense, again, there is a two-fold compo- tions of the whole; and these are the causes of sition; a natural and an artificial one.

different motions and sounds in the particles, Natural composition is that proceeding from which uniting compose the whole sound of the the manifold reflections of the first sound from string, and make a uniform composition, in adjacent bodies, where the reflections are not so which the tone of the particular part struck presudden as to occasion echoes, but are all in the vails, and all the others mix under a due suborsame tune with the first note. Artificial com- dination with it, so as to make the composition position, which alone comes under the musician's smooth and agreeable. If the parts be unevenly province, is that mixture of several sounds or irregularly constituted, the sound is harsh; which, being made by art, the ingredient sounds which is the case in what we call false strings, are separable and distinguishable from one ano and various other bodies, which, for this reason, ther. 'In this sense the distinct sounds of seve- have no certain and distinct tone, but a comporal voices or instruments, or several notes of the sition of several tones, which do not unite and same instrument, are called simple sounds, in mix, so as to have one predominant to specify contradistinction to the compound ones, in the total tone. As to clear and hoarse sounds, which, to answer the end of music, the simples they depend on circumstances that are accidental must have such an agreement in all relations, to the sonorous body; thus, a voice and instruchiefly as to acuteness and gravity, as that the ment will be hollow and hoarse, if raised within ear may receive the mixture with pleasure. an empty hogshead, that yet is clear and bright

Another distinction of sounds with regard to out of it: the effect is owing to the mixture of music is that by which they are said to be other and different sounds, raised by reflections, smooth and even, or rough and harsh, also clear which corrupt and change the species of the and hoarse: the cause of which differences de primitive sounds. For sounds to be fit to obtain


the end of music, they ought to be smooth and water, he calls, · By the mark five ! and as there clear, possessing especially the first quality: is no mark at four, six, eight, &c., he estimates since, without this, they cannot have one certain those nuinbers, and calls, ' By the dip four,' &c. and discernible tone. Dr. Burney remarks that If he judges it to be a quarter or a half more enquiries concerning the absolute production than any particular number, he calls, And a and modification of sound belong to physics; quarter five !'' And a half four !' &c. If he conwhereas a musician only examines sounds com ceives the depth to be three-quarters more than paratively one with the other, and considers their a particular number, he calls it a quarter less proportions and relation as divided into concords than the next : thus, at four fathoms and threeand discords.

fourths he calls, “A quarter less five !' and so The SOUNDBOARD is the principal part of an on. The deep sea-lead is marked with two knots organ. This soundboard, or summer, is a reser at twenty fathoms, three at thirty, four at forty, voir into which the wind, drawn in by the bel- and so on to the end. It is also marked with a lows, is conducted by a port vent, and thence single knot in the middle of each interval, as at distributed into the pipes placed over the holes twenty-five, thirty-five, forty-five fathoms, &c. of its upper part. This wind enters them by To use this lead more effectually at sea, or in valves, which open by pressing upon the stops deep water on the sea-coast, it is usual previousor keys, after drawing the registers, which pre- ly to bring to the ship, in order to retard her vent the air from going into any of the other course; the lead is then thrown as far as possipipes beside those it is required in.

ble from the ship on the line of her drift, so that, SOUNDBOARD, or SOUNDING-BOARD,, denotes as it sinks, the ship drives more perpendicularly also a thin broad board placed over the head of a over it. The pilot, feeling the lead strike the public speaker, to enlarge and extend or bottom, readily discovers the depth of the water strengthen his voice. Soundboards, in theatres, by the mark on the line nearest its surface. The are found by experience to be of no service; bottom of the lead being also well rubbed over their distance from the speaker being too great with tallow retains the distinguishing marks of to be impressed with sufficient force. But the bottom, as shells, ooze, gravel, &c., which soundboards immediately over a pulpit have often naturally adhere to it. The depth of the water, a good effect, when made of a just thickness, and the nature of the ground, which is called the and according to certain principles.

soundings, are carefully marked in the log-book, SOUNDING, the operation of trying the depth as well to determine the distance of the place of the sea, and the nature of the bottom, by from the shore as to correct the observations of means of a plummet sunk from a ship to the bot- former pilots. tom. There are two plummets used for this pur Sound Post, a post placed withinside of a pose in navigation, one of which is called the violin, &c. as a prop between the back and the hand-lead, weighing about eight or nine pounds, belly of the instrument, and nearly under the and the other the deep sea-lead, which weighs bridge. from twenty-five to thirty pounds.

SOUP, n. s. Sax. suppa; Fr. soupe ; Swed. shaped like the frustum of a cone or pyramid. soppa. Strong broth; a decoction of flesh for The former is used in shallow waters, and the the table. latter at a great distance from the shore; parti Spongy morells in strong ragouts are found, cularly on approaching the land after a sea voy. And in the soup the slimy snail is drowned. age. Accordingly the lines employed for this

Gay's Trivia.) purpose are called the deep-sea lead-line, and Let the cook daub the back of the footman's new the hand lead-line. The hand lead-line, which livery; or, when he is going up with a dish of soup, is usually twenty fathoms in length, is marked at let her follow him softly with a ladle full. Swift. every two or three fathoms; so that the depth of Soup, Portable, or Dry Soup, is a kind of the water may be ascertained either in the day cake formed by boiling the gelatinous parts of or night. At the depth of two and tẶree fathoms animal substances till the watery parts are evathere are marks of black leather; at five fathoms porated. This species of soup is chiefly used at there is a white rag; at seven a red rag; at ten sea, and has been found of great advantage. black leather; at thirteen black leather; at fif- The following is a receipt to prepare it : of calves teen a white rag; and at seventeen a red ditto. feet take four; leg of beef twelve pounds; knucSounding with the hand-lead, which is called kle of veal three pounds; and leg of mutton ten heaving the lead by seamen, is generally per- pounds. These are to be boiled in a sufficient formed by a man who stands in the main chains quantity of water, and the scum taken off as to windward. Having the line quite ready to usual ; after which the soup is to be separated run out without interruption, he holds it nearly from the meat by straining and pressure. The at the distance of a fathom from the plummet; meat is then to be boiled a second time in other and having swung the latter backwards and for- water; and the two decoctions, being added towards three or four times in order to acquire the gether, must be left to cool, in order that the fat greater velocity, he swings it round his head, and may be exactly separated. The soup must then thence as far forward as is necessary; so that, by be clarified with five or six whites of eggs, and a the lead's sinking whilst the ship advances, the sufficient quantity of common salt added. The line may be almost perpendicular when it reaches liquor is then strained through flannel, and evathe bottom. The person sounding then proclaims porated on the water-bath to the consistence of the depth of the water in a kind of song resem a very thick paste ; after which it is spread bling the cries of hawkers in a city. Thus if the rather thin upon a smooth stone, and cut into Inark of five fathoms is close to the surface of the cakes, and lastly dried in a stove until it becomes

Both are

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