We then quickly come to those transition formations, in which primeval nature, nature dead and purely mineral, seems to have disputed the empire with organising nature. Black limestones, and schists which present only crustacea and shells of kinds now extinct, alternate with remains of primitive formations, and announce our having arrived at those formations, the oldest with which we are acquainted, those ancient foundations of the present envelop of the globe, the marbles and primitive slates, the gneisses, and, lastly, the granites. Such is the precise enumeration of the successive masses with which nature has enveloped the globe. The positive geological information presented by it, has been obtained, by combining the knowledge furnished by mineralogy with that presented by the sciences connected with organic existence. This order, so new and so interesting in facts, has only been acquired by geology, since it preferred positive knowledge, furnished by observation, to fanciful systems, contradictory conjectures regarding the first origin of the globe, and all those phenomena, which, having no resemblance to what actually takes place in nature, could neither find in it, for their explanation, materials nor touchstone. A few years ago, the greater number of geologists might have been compared to historians, who, in writing the history of France, should have interested themselves only about the events which had taken place among the Gauls before the time of Julius Cesar. In composing their romances, however, these historians would have taken advantage of their knowledge of posterior facts; and the geologists of whom I speak, absolutely neglected the posterior facts, which could alone have reflected some light upon the darkness of preceding times. _Enumeration of the Fossil Animals recognised by the Author._ In concluding this discourse, there only remains for me now to present the result of my own researches, or, in other words, a general account of my great work. I shall enumerate the animals which I have discovered, in the inverse order of that which I have followed in my enumeration of the formations. By proceeding deeper and deeper into the series of strata, I there rose in the series of epochs. I shall now take the oldest formations,--make known the animals which they contain,--and, passing from one epoch to another, point out those which successively make their appearance in proportion as we approach the present time. We have seen that zoophytes, mollusca, and certain crustacea, begin to appear in the Transition formations; perhaps there may even at that period be bones and skeletons of fishes; but we do not by any means observe at so early a period remains of animals which live on land, and respire air in its ordinary state.