174 SOUND Nov. 10, 1808, took from the English Corunna (where he had heen at first defeated) and Fer- rol, and occupied Oporto and the northern part of Portugal, whence he was expelled by Wel- lington. After his retreat to Spain he gained several advantages, and on March 11, 1811, he obtained possession of Badajoz through the treachery of the Spanish commander ; but he was defeated by Beresford at Albuera, May 16, and Wellington carried Badajoz by assault with fearful loss on the night of April 6, 1812. Disapproving of 'King Joseph's proceedings, Soult asked to be relieved; but soon after reaching France Napoleon ordered him to as- sume the chief command of the army in Spain, and retrieve Joseph's crushing defeat at Vito- ria, June 21, 1813. But despite his wonderful efforts, after various engagements in the moun- tain passes with the main body of the allies, he was cut off from Bayonne by Wellington, de- feated at Orthez, Feb. 27, 1814, and forced back to Toulouse, which, was taken by Wel- lington, April 10. Soult offered a heroic re- sistance, and consented only to an honorable capitulation after the full confirmation of Na- poleon's first abdication, and led his troops safe- ly out of the city. His conduct during this memorable campaign received the warm com- mendation of Napier, the English historian of the peninsular war; and when 26 years later Soult officially attended the coronation of Queen Victoria, he was most cordially received by Wellington and his other former adversa- ries. Under the first restoration he was for a short time minister of war ; but as he rejoined Napoleon on his return from Elba, and served as major general at Waterloo, he was banished from 1816 to 1819. In 1820 he was reinstated as a marshal and received a pension of 200,000 francs, and in 1827 he became a peer. Under Louis Philippe he was minister of war in 1830- '31, prime minister in 1832-'4, and again (with the portfolio of foreign affairs in 1839-'40, and of war in 1840-'45) from 1839 till 1847, when the extraordinary title of marshal-general was given to him on his retirement. He left me- moirs, of which only the first part was pub- lished (3 vols., 1854) by his son Napoleon Hec- tor, who died in 1857. SOUND, the sensation peculiar to the organ of hearing. This sensation is the final effect of a closely connected series of mechanical actions, which have their origin in some rapid- ly vibrating body, whence they are propagated progressively through the air to the membrane of the drum of the ear, and thence, through a series of small articulated bones, into the in- ner cavity. This cavity, tunnelled in the hard petrous bone, is filled with liquid and contains the delicate terminal fibrils of the auditory nerve. Each of these fibrils appears to bo at- tached to the centre of a delicate rod or chord. These chords are stretched, and being of dif- ferent lengths and diameters are generally sup- posed to be tuned to sounds extending through a range of several octaves. By the sympa- thetic vibrations of these tuned bodies they shake their attached nerve fibrils and thus give rise to sensations peculiar to sounds of various pitch. From the foregoing we see that the subject of sound is naturally divided into three parts. In the first division we shall consider the manner of production of sound, and the nature of those vibrations which cause sono- rous sensations. In the second part we shall explain the manner in which these vibrations are propagated through the elastic medium existing between the vibrating body and the ear. In the third part we shall consider the manner in which the ear perceives a simple sound and analyzes a composite sound into its elementary sonorous sensations. At the place of origin of every sound there is always some solid, liquid, or gaseous body in a state of rapid vibration. This vibrating body imparts its motions to any elastic medium with which it may be in contact, and the vibrations thus given to the contiguous medium are propa- gated in all directions. The contiguous elastic medium may be a solid, a liquid, or a gas. Proofs of the above statements are readily afforded by the following simple experiments. A sounding tuning fork is drawn over a piece of smoked glass, so that the point of a piece of foil, attached to one of its prongs, may just touch the glass. After this experiment we observe that the point attached to the fork has laid bare the glass in a sinuous line, as seen in fig. 1, thus showing that when the fork causes FIG. 1. a sound its prongs are swinging to and fro in a direction perpendicular to its length. That a liquid may be the vibrating body at the source of the sound, is shown by placing a " siren " under water and forcing through it a current of water. If we take an organ pipe with glass sides and sprinkle in its interior a small portion of precipitated silica, we shall, on sounding the pipe, observe this very light powder rise in thin delicate vertical plates in certain portions of the pipe, while in intermediate places the silica remains at rest. Neither the tone of the pipe nor the positions of the plates of silica are altered in the least by pressure on the walls of the pipe ; thus showing that the real vibrating body in an organ pipe is its contained column of air. It now remains to show that the me- dium through which the sonorous vibrations are propagated outward from the vibrating body may be either solid, liquid, or gaseous. One of the most beautiful experiments in acoustics was invented by Sir Charles Wheat- stone, and shows that sounds, even the most complex, may be transmitted through solids as readily as through the air. In the lower
