11;
during tempestuous weather, has been known to take place even in a calm; but the
circumstance is singular. The waters, at those times, are seen to rise rapidly to the
height of about five feet, and to fall as suddenly, and thus successively for several hours;
while a rumbling noise is heard, not unlike tlie explosion or firing of distant guns. Many
have been the conjectures and suppositions of the Genevese naturalists to account for
this phsnomenon, which is no-where so conspicuous as near the extremities of the lake.
By some of those eminent men it has been ascribed to the effects of a sudden shock of the
wind; by others to the refoulement, or ebbing of the river Arve 5 while, again, others
have attributed it to the action of electrical clouds, which, when passing over the
lake, have by attraction raised the waters to the height above mentioned, and so produced
that kind of undulation. Now, as I do not exactly acquiesce in those ideas, I
shall here beg leave to state my own suppositions, having had frequent opportunities of
witnessing the effects of those seiches, and, like others, been tempted to search into
their cause.
From what I have observed, I have been induced strongly to suspect that this
singular effect may in some degree be ascribed to the currents which exist at the bottom
of the lake, independent of those of the rivers which throw themselves into it 3 as likewise
to the subterraneous air, called vandaise by the Genevese watermen,—which, by
rising to the surface of the lake, so frequently occasions storms; besides many other
causes, which I may in future endeavour to explain.
"Water spouts have also been observed to have risen on the lake to one hundred
and thirty toises above the surface of the water, in the shape of a funnel, extending
thirty-five toises in diameter, though happening at all times invariably where the depth
of water is the greatest, or between Meillerie, Lausanne, and Vevay.
These phsnomena do not often happen; but, when they do, ought assuredly to be
reckoned as curious as those which are now and then observable on the ocean.
The lake, in the environs of Geneva, as before mentioned, decreases both in width
and depth} and a quarter of a league from the harbour, or Cape Sécheron, to the
hills of Cologny, is crossed by a bank of argillaceous earth of tolerable thickness, at all
times covered by the water, though from seven to eight feet higher, and in some places
more, than the common or original bed of the lake. The abrupt state of its declivity,
and the chamfreted appearance of its border or edge, give it the exact resemblance of
a fissure experienced in that particular part; whereas, contiguous to Geneva, it is