the church, and was sent to the University of Edinburgh in 1767. After a few sessions, however, he quitted the divinity classes in order to study medicine. He was for a short time employed as surgeon to the dispensary at Bamborough Castle in Northumberland. Keturning to Scotland he took the degree of M.D. at St Andrews, on the 20th of May 1778. He now began to practise as a physician at Alnwick; but his general habits were rather those of speculation than exertion, and a moderate provision, acquired by his marriage with the daughter of Mr John Gray, of Alnwick, had emancipated him from the necessity of professional labour. In 1784 he finally returned to Edinburgh, where he continued to reside till the close of his life. For several years his attention was occupied with his edition of The Works of the British Poets, with Prefaces Biographical and Critical (14 vols. 8vo, Edin. 1792-1807). His other publications were, The Miscellaneous Works of Tobias Smollett, M.D., with Memoirs of his Life and Writings (Edin. 1796); Life of Samuel Johnson, LL.D., with Critical Observations on his Works (Edin. 1815); The Works of John Moore, M.D., with Memoirs of his Life and Writings (Edin. 1820); and The Grave and other Poems, by Robert Blair; to which are prefixed some Account of his Life and Observations on his Writings (Edin. 1826). Dr Anderson died on the 20th
Feb. 1830.
ANDES. The Andes form a mountain chain second only to the Himalayas in the vastness of its proportions, and possessing many remarkable peculiarities. The origin of the name appears to be unknown, although numerous meanings have been authoritatively assigned to it. It has been variously supposed to be derived from the Peruvian words Anta, or tapir; Anti, meaning metal or copper; and Ant-is, the name of a tribe resident in the mountains; or from the Spanish Andenes, applied to the gardens on the terraces which occur on the western slopes of the Andes in Chili. Humboldt believes its meaning has been lost. In connection with this may be noticed the curious fact mentioned by Colonel Tod, that the Hindoos of North India called the Himalayas by the name Andes.
The Andes form a continuous belt of mountainous high land along the western margin of South America, and have been considered by many writers as the southern continuation of the Rocky Mountains, which form a similar belt along the west side of North America. There are many objections against this view, and in favour of that which makes the Andes and Rocky Mountains two distinct ranges. In New Granada, or Columbia, as it is now called, the eastern range of the Andes terminates on the western side of the Gulf of Maracaybo, near 72 W. long. South of the gulf a branch range is thrown off, which traverses Venezuela, The central range dies out in the low lands south of the junction of the Cauca and Magdalena rivers. The western range also lowers and spreads in breadth in advancing northwards, and is lost in the low flats along the south margin of the Gulf of Darien. At the neck of the Panama isthmus, the Naipi and Cupica valleys stretch from the Atlantic to the Pacific Ocean, and are nowhere more than a few hundred feet above the level of the sea. North of the Atrato a serpentine ridge of mountains occurs, which terminates in Cape Tiburon. It is crossed by a pass called Tanela, which is about 5 miles in length, and 130 feet above the sea. Most of the isthmus between 8 and 9 N. lat. is below the level of this pass. Here the Isthmus of Panama curves round westwardly; and west of Panama there is another broad low tract stretching right across. This district cannot be regarded as belong ing in any way to the Andes. In Central America the mountains form numerous isolated ranges. In Mexico there are two high sierras. The eastern sierra does not reach the Rio Branco. The western sierra terminates at its north end in the Sierra Madre de Durango, which dies out in the northern part of Chihuahua and in Sonora, without being in any way connected with the Rocky Mountains.
The Rocky Mountains commence in about 100 W. long, at their south end, and terminate in about 145 W. at the north end, and have a general north-westerly direction. The Andes, on the other hand, commence near 54 S. lat. and 70 W. long. The southern portion forms a gentle curve, bending round to 73 W. in Patagonia, and reaching 70 again in the south of Chili. It continues on this line to Coquimbo, where it bends easterly, and after a slight double curve it cuts the meridian of 70 again south of Lake Titicaca. There is then a sharp bend, corresponding to that in the coast, which carries the range nearly to 80 W. in Ecuador, beyond which it again has an easterly bend, so as to cause it to terminate between 72 W. and 76 W. The north and south ends are consequently nearly in the same meridian. There are other dissimilarities between the Andes and the Rocky Mountains.
The formation of the Andes is due to several causes operating at distinct intervals of time. They consist mainly of stratified material which has been more or less altered. This material was deposited at the bottom of a sea, so that at some former time the highest portions were submerged, probably in consequence, to a certain extent, of subsidence of the sea bottom. Since the latest deposits there has been upheaval and denudation. The range, then, has resulted from the accumulation of sediment on a subsiding area ; from the subsequent upheaval of such deposits, which have been increased in height by the ejection of volcanic products; and from the operation of denuding agents.
probable that the Andes mark an area on which sedimentary deposits have been accumulated to a greater thickness than on any other portion of South America. It is further demonstrable that these deposits belong to several geological periods, the elevation having occurred at different periods, while their axes extend in different directions. Hence it is a complex range of mountains formed by the combination of several distinct systems of ridges. The width of the range varies from about 60 to 300 or more miles, biit, as compared with other mountains, the Andes are for the most part narrow relatively to their height. Where their special features are most characteristically developed, they consist of a massive embankment-like foundation, rising with a rapid slope from the low country on either side, and having its margins sitrmounted by lofty ridges of ragged or dome-like summits. These Cordilleras, as they are usually termed, flank longitudinal valleys, or plain-like depressions which form the highest levels of the central portion of the gigantic embankment, and which vary in width from 20 to 60 miles. At intervals the longitudinal depression is broken up, either by ridges connecting the Cordilleras, or by lofty plateau-like uplands. In several cases these transverse ridges and belts of high ground form the main watershed of the country. They are rarely cut across by the river systems, whereas both the marginal Cordilleras are intersected at numerous points, and more especially by the rivers draining the eastern slope of the country. In no case do these eastern rivers originate to the west of the western Cordilleras. A few of the central valleys, or plain-like depressions, have no connection either with the western or eastern river system. Roughly speak ing, the height of the central plains or valleys is from 6000 to 11,000 feet above the sea; of the passes and knots, from 10,000 to 15,000 feet; and of the highest
peaks, from 18,000 to 23,290 feet the last being the