SOUND. 



799 



an original sacred poem, in blank verse, under the 

 title of " Saul." His next work was of an en- 

 tirely different description, being principally sug- 

 gested by the admiration he felt, and the plea- 

 sure he derived, from the perusal of the poetical 

 writings of Scott, which induced him to com- 

 pose " Contance de Castillo, a metrical Poem 

 in ten cantos," published in 1810 : many of the 

 descriptive passages, and the spirit of the whole, 

 will show that he was not an unsuccessful imitator 

 of the romantic style of " Marmion," and " The 

 Lady of the Lake," then in the first freshness of 

 their justly deserved popularity. In 1814 he re- 

 published the " Orestes," together with four other 

 tragedies, one of which, called "Julian, or the 

 Confession," had already been represented at Drury 

 Lane ; and in 1815 a second corrected edition of 

 " The Georgics, with notes," appeared. 



In 181617, accompanied by his family, he 

 passed eighteen months in travelling through 

 France, Switzerland, and Italy, returning by Ger- 

 many. This tour gave rise to a series of poems, 

 many of which were composed on the spot, or ad- 

 dressed to some of the celebrated individuals with 

 whom he associated during his travels ; but, owing 

 to a variety of circumstances, they were not pub- 

 lished till some years after, under the title of 

 " Italy." After his return he employed himself in 

 revising his translation of the Georgics, and pre- 

 paring for the press a folio edition, published in 

 1827, containing the original text, and the transla- 

 tions of De Lille, Soave, Guzman, and Voss, to- 

 gether with his own. The summer and autumn of 

 1829 he spent in Scotland, about which time he 

 undertook a translation of the Iliad and Odyssey. 

 Early in 1831 the first edition of the translation of 

 the Iliad was published : and during the following 

 year he completed that of the Odyssey, and cor- 

 rected his version of the Iliad, preparatory to a 

 second edition. He lived to see this most favour- 

 ite employment finished and ready for publication, 

 embellished with engravings from the classical and 

 elegant designs of Flaxman. His death took place 

 on the 30th December, 1833, in the seventy-seventh 

 year of his age. 



SOUND. Mr William Shand has favoured us 

 with the following observations, which are in part 

 ex-tracted from a series of essays in the Medical 

 Gazette, commencing the 15th December, 1838, and 

 intended to illustrate the agency of sound in the 

 stethoscope and the human ear. 



Sir John Leslie observes that the doctrine of 

 sound is the most subtile and abstruse of any in 

 the whole range of physical science, and it must 

 be admitted that until a certain sequence of lead- 

 ing facts, and of the principles by which it is go- 

 verned, shall be ascertained, every attempt to ar- 

 rive at practical utility must in a great measure 

 fail, and can by possibility only succeed in a very 

 limited degree. 



I consider the following to embrace several of 

 the principles or laws which govern the pheno- 

 menon of sound, and as the only mode by which 

 these could be ascertained. I have endeavoured to 

 trace its operations in different bodies from its ori- 

 gin externally to the nerve of hearing, which is 

 the last vehicle of communication with the brain. 

 The two actions, and the laws by which they are 

 governed, are not alone material to the science of 

 acoustics, as regards the economy of speech, or the 

 agency of sound in the organ of hearing ; but 

 until these shall be understood and acted upon, per- 



turbation and derangement must prevail in all me- 

 chanism in a state of motion, from the magnetic 

 needle that defines our position on the globe, and 

 points out the mariner's way, to the ponderous train 

 and the metallic chords of the railway, which sup- 

 port and guide its course. 



1st. Sound is usually produced in bodies more 

 dense than the atmosphere, by sudden percussion, 

 and the action of one body upon another; and it 

 is considered to be the result of different modifi- 

 cations of matter only. 



2nd. Rapid agitation, causing the atoms or crys- 

 tals of a solid, by their extremities to act upon 

 each other, creates sound, whether this action be 

 occasioned by original impulse or by reflection. It 

 is regulated by the principles of attraction arid 

 repulsion ; and it cannot be produced, conducted, 

 or reflected, in any case, without being preceded 

 by vibratory action. 



3d. As the atoms or crystals of solids vibrate 

 repeatedly, and ultimately return to their primitive 

 positions, they produce more intense and continu- 

 ous sound than fluids, the component parts of which 

 pass each other and do not return to their original 

 positions. 



4tb. In conformity to the density of the atoms, 

 their form, and the medium distance between 

 them, is the intensity, duration, and velocity of 

 sound. 



5th. As all sonorous bodies, whilst they conduct, 

 or reflect, also create sound, it is obvious that to 

 preserve the original character of sounds, the re- 

 flecting or conducting body must in its movements 

 accord in time with those of the body which pro- 

 duces or forms the original sound. 



6th. As vibration is necessary to produce, con- 

 duct, or reflect, every still body must arrest sound, 

 on the same principle that a body at rest, being in 

 contact with a wheel moving round its axis, im- 

 pedes its progress. 



7th. Slow pressure compresses a few atoms only, 

 but rapid percussion occasions action, reaction and 

 sound, throughout hard bodies. 



8th. A solid, to produce much sound without 

 great impulse, must be of limited diameter in one 

 direction, for it vibrates most in this direction, be- 

 cause the atmosphere yields more than the solid. 



9th. In every sonorous body there are two dif- 

 ferent actions the tremulous or vibratory action, 

 which mainly creates sound ; and the undulating or 

 oscillating motion, which consists of a certain num- 

 ber of atoms moving together. 



10th. The undulation or oscillation by separating 

 the action of the atoms, also determines the dura- 

 tion of each distinct sound in a body, and in the 

 organ of hearing. In a string the nodal point 

 which separates the waves is easily defined, but in 

 an expanded thin body the termination of the wave 

 varies according to the form of the body, and is 

 not easily perceptible, and it is frequently irregular 

 in action and sound, so as to produce confusion in 

 the ear. 



For the reasons given, if a rod be struck on the 

 end, or a thin expanded body on the edge, little 

 sound is produced. 



llth. The chief distinction between hard solids 

 and fibrous substances is, that the latter possess 

 more of the adhesive and less of the repulsive 

 principle ; they require to be more distended in a 

 longitudinal and superficial direction ; and intensity 

 of sound is more by the extent of their excursions 

 than molecular action. 



