Some of the English _savants_ who had more specially devoted their attention to the study of this question, such as Messrs. Christy, Falconer, Carpenter, and Busk, went over to France, and in conjunction with Boucher de Perthes and several members of the Académie des Sciences of Paris, examined the exact locality in which the hatchets and the human jaw-bone had been found; they unanimously agreed in recognising the correctness of the conclusions arrived at by the indefatigable geologist of Abbeville.[5] This discovery of the hatchets and the human jaw-bone in the quaternary beds of Moulin-Quignon completed the demonstration of an idea already supported by an important mass of evidence. Setting aside its own special value, this discovery, added to so many others, could not fail to carry conviction into most minds. From this time forth the doctrine of the high antiquity of the human race became an acknowledged idea in the scientific world. Before closing our historical sketch, we shall have to ask, what was the precise geological epoch to which we shall have to carry back the date of man's first appearance on this our earth. The beds which are anterior to the present period, the series of which forms the solid crust of our globe, have been divided, as is well known, into five groups, corresponding to the same number of periods of the physical development of the earth. These are in their order of age: the _primitive rocks_, the _transition rocks_, the _secondary rocks_, the _tertiary_ and _quaternary rocks_. Each of these epochs must have embraced an immense lapse of time, since it has radically exhausted the generation both of animals and plants which was peculiar to it. Some idea may be formed of the extreme slowness with which organic creatures modify their character, when we take into consideration that our contemporary _fauna_, that is to say, the collection of animals of every country which belong to the geological period in which we exist, has undergone little, if any, alteration during the thousands of years that it has been in being. Is it possible for us to date the appearance of the human race in those prodigiously-remote epochs which correspond with the primitive, the transition, or the secondary rocks? Evidently no! Is it possible, indeed, to fix this date in the epoch of the tertiary rocks? Some geologists have fancied that they could find traces of the presence of man in these tertiary rocks (the miocene and pliocene). But this is an opinion in which we, at least, cannot make up our minds to agree.