We consider that there ought to be an entire revolution in the system of geological research; it ought to commence at ancient times, and come down to the present day, not _vice versâ_; we ought, in fact, to substitute synthetic for analytical geology. After having carefully noticed contemporaneous phenomena, we should doubtless be in time able to read simply the trace of a feeble revolution in the geological past, accomplished under the government of the same forces which are daily preparing new lands, new elevations, new depressions, and a new organic world on the surface of the globe, for the future. If it is probable that the atmosphere has changed within certain limits, if the nature of the waters has also been altered,--at least all these geological phenomena, these abysses, chains of mountains, and submerged continents, can only be the result of the forces now at work under our own eyes,--the comparison of animals which formerly existed with those which exist at the present day, shows, as we shall see farther on, that the conditions of life have not sensibly changed on the surface of the globe since the formation of the rocks subjacent to the metamorphous rocks. We deny that the earth is actually passing through a period of repose, and we do not believe that it has ever formerly been more disturbed. Since the age of the first vestiges of the organic life, which we find in the most ancient rocks, we think that our planet has not ceased to move in a calm and continuous march of existence; we think, in fact, that geological phenomena of all sorts, which we hear of now-a-days, are the exact history of the past, during which some volcanic phenomena have also taken place, but in an entirely sporadic manner. “The day is, perhaps, not very distant,” said M. Lartet, at the Institute,[310] in 1858, “when it will be proposed to strike out the word ‘flood’ from the vocabulary of positive geology.” This day approaches still nearer.[311] Before mooting, in our turn, a theory about the vertebrate animal kingdom (the only one which ought to occupy our attention) on the surface of the globe, we simply ask, what is meant by Étienne Geoffroy by the words _some considerable time_? This is a difficulty, we own, and we have just said so. We wish that the thirty thousand years,[312] the maximum time which we give to the farthest origin of man, should be considered as being the age which separates us from the first organic matter cast into the bosom of the waters, in the same proportion as the radius of the earth is to the distance which separates our sun from the most distant star of the most distant nebulous system which the best telescope can observe. The extent alone of the heavens can give us an idea of the extent of the past.