But this conclusion does not rest upon antecedent probability alone. We have proof unquestionable that a process such as we have described is actually going on. In the dredging of the river Thames large masses of solid Conglomerate are found from time to time, firmly compacted together by a ferruginous cement. And there is internal evidence that the process of solidification has been effected by natural causes within historic times; for it happens not unfrequently that Roman coins and fragments of pottery are found embedded in the solid block of stone. Similar discoveries were made in deepening the bed of the river Dove in Derbyshire, about the year 1832. Thousands of silver coins were found about ten feet under the surface, firmly cemented into a hard Conglomerate. Several of these coins bear dates of the thirteenth and fourteenth centuries; and therefore the pebbles which form the rock must have been deposited and converted into a solid mass since that time. But we must not suppose that so long an interval is necessary for the consolidation of rocks. In the early part of the present century a vessel called the Thetis was wrecked off cape Frio on the coast of Brazil. A few months afterward, when an attempt was successfully made to recover the dollars and other treasures which had gone to the bottom with the wreck, they were found completely enveloped in solid masses of quartzose Sandstone. The materials of the newly-formed stone were in this case manifestly derived from the granite rocks of the Brazilian coast.[38] In many parts of the Mediterranean, and along its shores, this process is known to be going on with equal rapidity. “The new-formed strata of Asia Minor,” writes Sir Charles Lyell, “consists of stone, not of loose, incoherent materials. Almost all the streamlets and rivers, like many of those in Tuscany and the south of Italy, hold abundance of carbonate of lime in solution, and precipitate Travertine, or sometimes bind together the sand and gravel into solid Sandstones and Conglomerates; every delta and sandbar thus acquires solidity, which often prevents streams from forcing their way through them, so that their mouths are constantly changing their position.”[39] In the Museum at Montpelier is exhibited a cannon embedded in a crystalline calcareous rock which was taken up from the bed of the Mediterranean near the mouth of the Rhone.[40]