UNFORESEEN EFFECTS OF DRAINING AND LOWERING LAKES. 355 
into decay, and though numerous attempts were made to re¬ 
pair it during the Middle Ages, no tolerable success seems to 
have attended any of these efforts, until the present gen¬ 
eration. 
Works have now been some years in progress for restoring, 
or rather enlarging and rebuilding this ancient tunnel, upon a 
scale of grandeur which does infinite honor to the liberality 
and public spirit of the projectors, and with an ingenuity of 
design and a constructive skill which reflect the highest credit 
upon the professional ability of the engineers who have planned 
the works and directed their execution. The length of this 
tunnel is 18,634 feet, or rather more than three miles and a 
half. Of course, it is one of the longest subterranean galleries 
yet executed in Europe, and it offers many curious particulars 
in its original design which cannot here be described. The 
difference between the highest and the lowest known levels of 
the surface of the lake amounts to at least forty feet, and the 
difference of area covered at these respective stages is not 
much less than eight thousand acres. The tunnel will re¬ 
duce the water to a much lower point, and it is computed 
that, including the lands occasionally overflowed, not less than 
forty thousand acres of as fertile soil as any in Italy will be 
recovered from the lake and permanently secured from inun¬ 
dation by its waters. 
Many similar enterprises have been conceived and ex¬ 
ecuted in modern times, both for the purpose of reclaiming 
land covered by water and for sanitary reasons.* They are 
sometimes attended with wholly unexpected evils, as, for ex¬ 
ample, in the case of Barton Pond, in Vermont, and in that 
of the Lake Storsjo, in Sweden, already mentioned on a former 
* A considerable work of this character is mentioned by Captain Gilliss 
as having been executed in Chili, a country to which we should have 
hardly looked for an improvement of such a nature. The Lake Taguataga 
was partially 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 covered by it were gained for cultivation.— U. S. Naval Astronomical 
Expedition to the Southern Hemisphere , i, pp. 16, 17. 
