Mr. Skertchly, of the Geological Survey of England, has furnished still another estimate, based on the growth of the Fen-beds on the east coast of England. It is sufficient to state that he also arrives at an estimate of about seven thousand years for the Neolithic period.21 Now these results are interesting, and their substantial agreement is, to say the least, striking. We must remember, however, that none of them are free from error. They may serve to clear up our thoughts on this subject, but we notice they tell us nothing as to the beginning of the Neolithic Age. Abandoning the effort to obtain dates for the various ages, attempts have been made to calculate the entire interval that has elapsed since the close of the Glacial times, and thus set bounds to the first appearance of Neolithic man. We briefly touched on this question in determining the antiquity of the Paleolithic Age, and we say, as far as this country was concerned, it was comparatively a recent thing, but as for Europe, it must be at a very remote time. M. Quatrefages has called our attention to two investigations in Europe, which, in order to understand this question, we will now glance at. The waters of the Rhone carry into Lake Geneva every year quantities of sediment. In other words, from this and other sources, the lake is gradually being filled up. Carefully calculating the amount carried into the lake in a year, estimates have been made of the length of time it has taken the river to fill up the lake as much as it has. But in making this calculation the date arrived at was a maximum one—that is, a point beyond which it is not reasonable to suppose the time extended. These calculations gave as a result one hundred thousand years. The meaning of this is that the time elapsed since the close of the Glacial Age was something less than the number just stated. On the other hand, a minimum date for this time has been obtained by estimating the amount of erosion in the valley of the River Saone, in France. From this we know that the time can not be less than seven thousand years.22