Phenomena which occur in various lakes in Europe, may be adverted to in support of this theory. The waters of lake Zirchnitzer, in the Dutchy of Carniola, in Germany, flow off, and leave the basin empty; and again fill it, in an extraordinary and impetuous manner; bringing up with its waters fish and even sometimes wild water fowl.[32] In the same country, there is a subterranean lake, in the Grotto Podspetschio, of considerable extent; the whole of this vast body of water, at certain times, will disappear in a few minutes, and leave the basin dry; and after a few weeks, it again suddenly returns, with a frightful noise. The lake of Geneva, and some others in Switzerland, at certain times rise and fall several feet without any cause, which has as yet been satisfactorily explained; and some writers inform us, that those lakes, particularly Geneva, send forth, at times, a grumbling noise. In the Saian mountains, near the source of the Yenisei, is a lake, called Boulamy-Koul, which, at the approach of winter, emits strange sounds, somewhat similar to those which precede the eruption of a volcano, and which are compared by the neighbouring inhabitants to howling. The inhabitants on the borders of Baikal, also state, that they have often heard dreadful and terrific howlings proceed from that lake.[33] The lake, Agnano, in Italy, sometimes, especially when the waters are high, appears to boil at its borders. This ebullition is supposed to be occasioned by some gaseous fluids, discharged into the bottom, which traverse the waters of the lake.[34] These various phenomena, which cannot be easily accounted for, might be best explained perhaps, on the principles of _mid-plane-spaces_. In various parts of the north, thick strata of ice are found, under a thick soil; and on ice-bergs, floating in the ocean, have been discovered masses of earth, of granite, and of other rocks.[35]