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by external pressure, or internal expansion of aerial or igneous fluid, of the vaulted roof thatcovered the immense subterraneous cavern or caverns, since forming the Lake of Geneva , tookplace; for the above thin irregular strata, filled with marine fossils, and the hills which now lieat the foot of the same mountains, wear visible marks of having been the last works of the sea.

Besides these instances, many others might be enumerated, which are as curious in themselvesas they would be interesting to the geologist; as, for example, 1st, the variety of species of sand-stone, as well as beds of sand and pebbles, found on the Saleve and the sides of the Voirons;2dly, the pyramidical form of the Mole, another stupendous mountain, which has also everypossible appearance of having likewise been the work of some rapid or impetuous current, whichhas, as it were, sharpened its summit, given to it that regular slope next the lake, and extremeabruptness on its southern side; 3dly, the apparent analogy which exists in both the structure andformation of the mountains of Sion and Jorat, which seem to have also been the drain of thatextensive lake; 4thly, the different species of gypsum found along the banks of the Rhone andnear the hills of Cologny , which may be entirely attributed to a mixture of calcareous and vitriolicearths, kept originally in a state of dissolution by the sea; 5thly, the existence of coal-pits onthe Saleive, contiguous to the valley of Monetier, though in truth not extensive; fithly, the salt-springs at Bex and Aigle, which are again evident proofs that the sea, beyond a possibility ofdoubt, once covered that part of the Alps , and that, from having at its last, retreat gradually. evaporated, it doubtless left, in several places, different masses of marine salt, some in gems or salgemmce solidum, and others in fossils, mixed with selenitous earth, which in all probability have,in process of time, given birth to these saline springs; finally, the bank called LeTravers, in greatpart covered with sand and pebbles, as noticed in the description of Geneva, and situated in the

lake, at about a quarter of a league from the harbour, I likewise consider as the remains of the

vaulted roof which covered the identical subterraneous cavern or caverns, now replaced by thelake,—and which having since been re-covered as well as the rest of the gulf, by the successivesediments carried from the summit of the Alps by the sea, as well as by rivers, the bed of the lake

has, in length of time, been formed nearly as it now is; but that the bank itself, having in its

principle a greater elevation than the other part of the bed, has consequently continued to pre-serve it.

Knowing of what importance to geology such hypothetical reasonings may be deemed, I mustfreely acknowledge that they merit a more extensive detail, strengthened by a greater number offacts and data than the plan of the present work will admit; but as I have already noticed that tobe my intention at a future day, in an Appendix , I now only wait for the completion of myTableau des Alpes, and again to re-visit the Cottian Alps (which lam now on the point of doing),in order to make new observations, and accomplish my promise.

Should I however be found, by the above remarks, to have in any degree contributed to theentertainment or instruction of that class of readers for whom this chapter has been written, I shallthink myself abundantly rewarded.

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