30. Reddish vitrifiable sand 15 0 -------- Total depth 101 0 -------- I have before said that I tried all these matters in aquafortis, because where the inspection and comparison of matters with others that we are acquainted with is not sufficient to permit us to denominate and range them in the class which they belong, there is no means more ready, nor perhaps more sure, than to try by aquafortis the terrestrial or lapidific matter: those which acid spirits dissolve immediately with heat and ebullition, are generally calcinable, and those on which they make no impression are vitrifiable. By this enumeration we perceive, that the soil of Marly-la-ville was formerly the bottom of the sea, which has been raised above 75 feet, since we find shells at that depth below the surface. Those shells have been transported by the motion of the water, at the same time as the sand in which they are met with, and the whole of the upper strata, even to the first, have been transported after the same manner by the motion of the water, and deposited in form of a sediment; which we cannot doubt, as well by reason of their horizontal position, as of the different beds of sand mixed with shells and marl, the last of which are only the fragments of the shells. The last stratum itself has been formed almost entirely by the mould we have spoken of, mixed with a small part of the marl which was at the surface.