439 CONSEQUENCES OF DRAINING LAKES. 
very ancient construction, and the Valle-Riccia appears to have 
once been the basin of a lake long since laid dry, but whether 
by the ‘bursting of its banks or by human art we are unable 
to say. 
The success of the Lake Celano tunnel has suggested other 
like improvements in Italy. A gallery has been cut, under cir- 
cumstances of great difficulty, to drain Lake Agnano near 
Naples, and a project for the execution of a similar operation 
on the Lake of Perugia, the ancient Trasimenus, which covers 
more than 40,000 acres, is under discussion. 
Many similar enterprises have been conceived and executed 
in modern times, both for the purpose of reclaiming land 
covered by water and for sanitary reasons.* They are some- 
times attended with wholly unexpected evils, as, for example, 
in the case of Barton Pond, in Vermont, and in that of a lake 
near Ragunda in Sweden, already mentioned on a former page. 
Another still less obvious consequence of the withdrawal of 
the waters has occasionally been observed in these operations. 
The hydrostatic foree with which the water, in virtue of its 
specific gravity, presses against the banks that confine it, has a 
tendency to sustain them whenever their composition and text- 
ure are not such as to expose them to softening and dissolu- 
tion by the infiltration of the water. If, then, the slope of the 
banks is considerable, or if the earth of which they are com- 
* A considerable work of this character is mentioned by Captain Gilliss as 
having been executed in Chili, a country to which we should hardly have 
looked for an improvement of such anature. The Lake Taguataga was par- 
tially drained by cutting through a narrow ridge of land, not at the natural 
outlet, but upon one side of the lake, and eight thousand acres of land cov- 
ered by it were gained for cultivation.—U. S. Naval Astronomical Expedi- 
tion to the Southern Hemisphere, i., pp. 16, 17. 
Lake Balaton and the Neusiedler See in Hungary have lately been, at least 
partially, drained. 
The lakes of Neuchatel, Bienne, and Morat, in Switzerland, have been con- 
nected and the common level of all of them lowered about four feet. The 
works now in operation will produce, in the course of the year 1874, a further 
depression of four feet, and recover for agricultural use more than twelve 
thousand acres of fertile soil. 
