Therefore we should expect to find, if we digged down in the earth, or in any portion of the earth which had undergone these changes, some traces of them. For example, if at one time the sea covered England for thousands or hundreds of thousands of years, depositing the remains of millions of animals on the sea's bottom during that period, we should expect to find some traces of these remains--perhaps in the form of chalk, seeing that the bones and shells of fishes dwelling in the sea contain a good deal of lime. Or again, if a forest covered England and grew and decayed there, not merely for a period like that which has elapsed since the Romans first set foot in Britain, but for a hundred times as long, we should expect to find some sort of vegetable deposit, hardened most probably by other layers above it. Do we? Well, coal is a vegetable deposit. If there was a time when ice covered the land we should expect to find traces of that; if a time when the land was desert; or when it was a lake--each and every one of these periods ought to leave some remains, some epitaph of itself. So they do. Let us for a moment consider with Sir Archibald Geikie[1] the subsoil beneath cities that have been inhabited for many centuries. In London, for example, when excavations are made for drainage, building, and other purposes, there are sometimes found, many feet below the level of the present streets, mosaic pavements and foundations, together with earthern vessels, bronze implements, ornaments, coins, and other relics of Roman time. Now if we knew nothing from actual authentic history of the existence of such a people as the Romans these discoveries deep beneath the surface of modern London would prove that long before the present streets were built the site of the city was occupied by a civilised race which employed bronze and iron for the useful purposes of life, had a metal coinage, and showed not a little artistic skill in its pottery, glass, and sculpture. But down beneath the rubbish wherein the Roman remains are embedded lie gravels and sands from which rudely fashioned human implements of flint, arrow-heads, hammers, and the like have been obtained. From that we learn that before the Romans came an earlier race had been there which employed weapons and instruments of roughly chipped flint. [Footnote 1: Sir Archibald Geikie's _Introduction to Geology_.]