Page:The American Cyclopædia (1879) Volume XVI.djvu/419

VOITURE jury to the nerve and the consequent paraly- sis of the laryngeal muscles. The same effect is produced by injury or compression of the pneumogastric nerves in the neck, above the point where their recurrent laryngeal branches are given off. The voice is also affected by inflammation, thickening, ulceration, or sub- mucous infiltration of the tissues of the larynx ; all these causes interfering with the necessary action of the laryngeal muscles and the forma- tion of a vibrating fold of mucous membrane at the rima glottidis. There is also a form of hysterical affection in which the power of forming a vocal sound is temporarily lost, owing to a functional disturbance of innerva- tion, and consequent failure of action in the laryngeal muscles. Loss of voice from any of these causes is termed aphonia, and is to be distinguished from aphasia, an affection of different origin, in which the patient retains the power of making a vocal sound, but is un- able to remember the appropriate words or phrases necessary to communicate his ideas. (See BRAIN, DISEASES OF THE, vol. iii., p. 203.) VOITURE, Vincent, a French poet, born in Amiens in 1598, died in or near Paris, May 27, 1648. Though attached to Gaston of Orleans, he was employed in Italy by Eichelieu; and under the regency of Anne of Austria he held several sinecures at the court. His passion for gambling and amours involved him in various difficulties. He was a leader in the society of the hotel Rambouillet, and one of the original members of the French academy. His letters and poems first appeared in 1649, and they are included in the Collection Charpentier, with notes by Ubicini (2 vols. 18mo, 1855). VOLATILE OILS. See ESSENTIAL OILS. VOLCANO (Lat. Vulcanus, the god of fire), an opening in the crust of the earth from which are ejected heated gases, steam, finely divided solid matter resembling ashes, cinders, masses of solid rock intensely heated, and currents of molten rock called lava. These materials in time build up a conical pile, which may attain a height of several thousand feet, forming a volcanic hill or mountain around the opening, and having in its upper part a depression called the crater of the volcano, which communicates with the source of the fiery matters below. The action of certain of these volcanic vents or openings is continuous or nearly so, one or all of the products named being daily ejected, while in others eruptions take place only at rare intervals. Those which are supposed to have ceased to be active are called extinct vol- canoes. The name of mud volcanoes is given to openings which through the action of steam or gas throw up a pasty mixture of earth and water unaccompanied by any igneous mani- festations. Volcanic vents sometimes appear on high lands, and in this way their cones may be built up on mountains of ordinary rocks, while at other times the whole elevation from the sea level is of volcanic origin. They occa- sionally break out beneath the sea, forming 822 VOL. xvi. 26 VOLCANO 399 submarine volcanoes, the matters ejected from which sometimes build up islands. Volcanic activities have been at work on the earth's sur- face from, early geological times ; but modern volcanoes are limited to certain regions, gen- erally very distinct from those which were the seats of volcanic energy in past geological pe- riods. On the American continent modern volcanoes are limited to the Pacific slope, along which they may be traced almost continuously from Cape Horn to Alaska. Great numbers of volcanoes occur throughout the Andes, where some attain immense heights, as Cotopaxi in Peru, about 19,500 ft. above the sea (accord- ing to Dr. Reiss, who ascended it in 1872). The volcanoes of Central America and of Mexico are numerous and conspicuous, and in California and Oregon we have Shasta, Hood, and St. Helen's, attaining heights of from 11,- 000 to more than 14,000ft. Mt. St. Elias, in Alaska, is about 18,000 ft. high. Through the Aleutian islands the belt of volcanoes of western America is connected with those of Kamtchatka, which, with those of the Kuriles, of Japan, and of the Philippines, form inter- rupted chains of volcanic vents to the burning mountains of the Indian archipelago. In south- ern continental Europe there are numerous ex- tinct volcanoes ; but with the exception of Ve- suvius the active vents are now confined to the islands of the Mediterranean. Besides Etna and Stromboli, there are many volcanic islands in the eastern parts of the Mediterranean, while further eastward in continental Asia are lofty volcanic peaks about the Red sea and the Cas- pian, on the shores of which is Demavend, 20,- 000 ft. high. Beyond this in the Thian-shan mountains a small volcanic region is said to exist. In Africa there are numerous volcanic vents in the eastern ranges about the equator, besides which a single volcano is known on the western coast at the bight of Benin, near which are also some volcanic islands. In the Atlantic are Jan Mayen and. Iceland, remarkable for volcanoes, the volcanic islands of the "West In- dies, and those of the Azores, Madeira, the Canaries, the Cape Verd islands, St. Helena, and Tristan d'Acunha. There are great num- bers of volcanoes throughout the North and South Pacific, the most remarkable of which are those of the Hawaiian islands. Volcanoes occur in Few Zealand, in southern Australia, in the Indian ocean, and further south in the Antarctic seas, where remarkable burning mountains have been seen. It is impossible to determine with any degree of accuracy the number of existing volcanic vents. Humboldt fixed it at 407, of which 225 had been active within a century. Of the latter about half were supposed to be upon the Asiatic islands. It has since been estimated that the Indian archipelago alone contains over 900. A no- ticeable fact in the history of volcanoes is their general linear arrangement, which is particu- larly conspicuous in the ranges of volcanic isl- ands of eastern Asia and in those of the west-