570 THE FRESH-WATER LOCHS OF SCOTLAND 
says that both lakes are remnants of a vast inland sea, which once 
existed in this region, extending from lat. 15° to 21° S., and draining 
by a large river into the basin of the Amazon. Both lakes have 
been rapidly drying up within historic times. The old temple, which 
was once on the shores of Titicaca, is now a considerable distance 
away from it, and some height above the level of the waters. Sir 
Martin Conway^ says that somewhere on the borders of Bolivia and 
Chili, at an altitude of 17,000 feet, are the remains of cultivated fields 
now abandoned. In South America no fields at a height of 17,000 
feet can be cultivated, so that the abandonment of these fields was 
due to the great increase in elevation that had occurred within historic 
times in the district. This increase in elevation appears to apply, 
according to Sir Martin Conway, to the central belt of plateau that 
runs north and south through a considerable part of South America. 
Along the Peruvian slope shells of existing species are found on the 
hillsides at an altitude of 1000 or 1500 feet, and even, according to 
some authorities, as high as ^000 feet. The increasing desiccation of 
the plateau is due to that rapid elevation. The moisture comes in 
a steady drift from the east over the great Amazon plain, and is 
precipitated upon the mountains. As the mountains increase in 
altitude, and the belt of mountainous country widens, the rainfall on 
the actual plateau diminishes. 
Lake Titicaca is situated between lat. 15° 20' and 16° 35' S., 
and between long. 68° 15' and 69° 40' W. It is the highest lake of 
America, lying 12,500 feet above sea-level. Its length is 120 miles, its 
maximum breadth 41 miles, and its area about 3200 square miles, 
exclusive of islands. About 120 soundings were taken by Neveu- 
Lemaire,^ the Belloc sounding machine being employed whenever the 
depth was greater than 32 feet. In his bathymetrical map the 
contours of 25, 100, and 200 metres (82, 328, and 656 feet) are drawn 
in. The deepest area lies towards the north-east shore, the contour- 
line of 200 metres approaching comparatively close in two places, 
while on the opposite side a wide band of regular width, with depths 
of 100 to 200 metres, runs parallel to the south-west shore. Soto 
Island, the midmost island in the lake, rises abruptly from the deepest 
part, 270 metres (886 feet) being found at a little distance from its 
south end on the landward side, while the maximum depth got by 
Lemaire (272 metres or 892 feet) was found abreast of the island on 
the major axis of the lake.^ The " Little Lake,'' joined to the " Great 
1 See discussion on tlie desiccation of Eur-Asia, Geogr. Journ., vol. xxiii. 
p. 736, 1904. 
2 See Neveu-Leniaire, Les lacs des hauts 'plateaux de I' Amerique Sud, Paris, 1906. 
2 Agassiz gives 154 fathoms (924 feet) as the maximum depth ("Hydro- 
graphic Sketch of Lake Titicaca," Proc. Amer. Acad., vol. xi. p. 283, 1876). 
