Ch. XVIII. ] 



LAKE OF GENEVA. 



417 



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for, in the case of a lake, it is obvious that these must consist 

 exclusively of such genera of animals as inhabit the land or 

 the waters of a river or lake ; whereas, in the other case, 

 there will be an admixture, and most frequently a predomi- 

 nance, of animals which inhabit salt water. In regard, 

 however, to the distribution of inorganic matter, the deposits 



formed 



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stances. 



>/ 



Lakes exemplify the first reproductive 



operations in which rivers are engaged when they convey the 

 detritus of rocks and the ingredients of mineral springs 

 from mountainous regions. The accession of new land at 

 the mouth of the Ehone, at the upper end of the Lake of 

 Geneva, or the Leman Lake, presents us with an example of 

 a considerable thickness of strata which have accumulated 

 since the historical era. This sheet of water is about thirty- 



, and its breadth is from two to eight miles. 

 The shape of the bottom is very irregular, the depth having 

 been found by late measurements to vary from 20 to 160 

 fathoms."* The Ehone, where it enters at the upper end, is 

 turbid and discoloured ; but its waters, where it issues at the 

 town of Geneva, are beautifully clear and transparent. An 

 ancient town, called Port Vallais (Portus Valesige of the 

 Eomans), once situated at the water's edge, at the upper end, 

 is now more than a mile and a half inland — this intervening 

 alluvial tract having been acquired in about eight centuries. 

 The remainder of the delta consists of a flat alluvial plain, 

 about five or six miles in length, composed of sand and 

 mud, a little raised above the level of the river, and full of 

 marshes. 



Henry 





numerous soundin 



in all parts of the lake, that there was a pretty uniform depth 

 of from 120 to 160 fathoms throughout the central region, 

 and on approaching the delta, the shallowing of the bottom 

 began to be very sensible at a distance of about a mile and 

 three quarters from the mouth of the Ehone ; for a line 



St. Gingoulph to Vevey gives a mean depth of 



drawn from 



vol. i. 



* De la Beche, Ed. Phil. Journ. vol. ii. p. 107. 



Jar. i;;o. 



E E 



