OF LAKE-BASINS. 657 



while comparing the perpendicular or transverse valleys on the southern 

 sides of the Alj)s and Himalayahs. 



Take the Lago Maggiore, which is about 52 English miles long, and 

 oi to 4 miles wide, at the broadest part of the central portion between 

 Luino and Laveno. It is fed by the Ticino, consisting of two main 

 branches given off across the strike of the chain. The basin forms a 

 long, narrow, flexuous hollow, bounded by low hills, but open to the 

 south. Its greatest depth, opposite Santa Caterina, at one of its con- 

 tractions, about 12| miles from its southern extremity, is 2,605 feet, 

 giving a general gradient of about 200 feet per mile for the rise of the 

 bottom to the surface between the two points. Taking Lynch's esti- 

 mate for the Dead Sea (1,308 feet), the extreme depth of the chasm 

 occupied by water in the Lago Maggiore is double that of the former, 

 and the depression of its bottom below the surface of the Mediterranean 

 is 1,927 feet, being only about 678 feet less, or the height of the lake 

 above the sea-level. It is even deeper than any soundings yielded in 

 the Gulf of Genoa (vide Admiralty Chart). 



The basin of the Lago di Lugano is so irregular in form, branched, 

 and ' polype-like ' — to use the phrase of Desor — that its erosion by a 

 pro p ssive glacier is not easily conceivable, but is readily so on the sup- 

 position of an intersection of fissures combined with aqueous erosion. 



The Lago di Como is about forty miles long, and its body or northern 

 half three miles wide ; its surface above the sea-level is 695 feet; its 

 greatest depth is 1,926 feet. Near the middle it divides into two long 

 diverging arms (like the legs of a pithed frog), pointing southwards, and 

 separated by the promontory of Bellaggio. The distance across between 

 Lecco and Como, the extremities of the two branches, is no less than 

 fifteen or sixteen miles. Upon the glacier-erosion hypothesis how is 

 this great fork to be explained ? If the glacier of the Adda Valley was 

 adequate to the erosion of the profound lake, how did it spare the com- 

 paratively insignificant barrier of the promontory and separate into two 

 diverging branches ? If physical features are to be admitted as of any 

 weight in the argument, it would seem as clear that the fissures existed 

 before the descent of the glacier as if the eye of man had witnessed the 

 fact. 



The Lago di Garda, the largest of the Italian lakes, is about fifty-five 

 miles long. Its form is irregularly gourd-like, the northern part or 

 neck being three or four miles wide, and the southern or expanded 

 portijn fifteen miles, the whole covering an area of about 140 square 

 miles: surface 227 feet above the Adriatic. Its depth is variously 

 stated, as being 951 feet (L\ de Beaumont), and 1,992 feet (Murray's 

 Hand-Book). The latter would be most in accordance with the depths 

 of the lakes Maggiore and Como, the Adriatic, as far south as Ancona, 

 nowhere exceeding fifty-nine fathoms. The basin is bounded on the 

 south by the enormous moraine stretching across between Lonato and 

 Sommacampagna. Although now fed by the Sarca, and disconnected 

 from the Adige, it was the great glacier of the latter valley which 

 formerly contributed most to fill the basin of the Garda. A remarkable 

 point in the physical geography of the case, and bearing on the argu- 

 ment, requires to be noticed. The Valley of the Adige, with the ex- 

 ception of the Pass of Calliano, is very open between Trent and 

 Roveredo, and more especially open on its west side towards the Valley 



VOL. II. V V 



