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I have come by calculating from the mean depth of neolithic finds in Norwegian peats, but this computation has not quite so much importance, though the fact that the generally adopted archeological chronology agrees as well with geological estimates certainly has some weight.

I shall recall the fact that calculations on the length of post-glacial time based on the receding Niagara, St. Anthony Falls, or the Michigan lake shore, on boulder pedestals in Scotland, the denudation of the Somme, the Plume creek, or the Raccoon valley, deposition of the Tinière or the Rhone, etc., delta, the thickness of glacial clay in New Hampshire and in Sweden, the rate of growth of peat in North America and Ireland, the atmospheric waste of the Parallel roads on Lochaber, the depth of some ancient neolithic finds, that all these give numbers of about the same value, 5,000 to 12,000 years. Doubtful as some of these chronometers may be, all fair chances are against any supposition which differs in any considerable degree from those of about thirty independent estimates I have got together. With full regard to a legitimate calculation of probabilities, it may be predicated that the number of 7,000 to 10,000 years is as nearly an exact estimate of the duration of post-glacial time as can ever be expected.

It is now tempting to try a comparison between the subglacial and the epiglacial terraces and lakes in Norway. When the much greater eroding force of the epiglacial glaciers is properly reduced, I do not think it can be very much at variance with the truth to compute the epiglacial period to be between five and ten times the duration of the subglacial, the smaller number being somewhat more probable. We would then get 10,000 to 20,000 years for the epiglacial period and perhaps 15,000 to 25,000 for the whole deuteroglacial time. For the interglacial period, the Norwegian geology cannot as yet give any reliable measure but the depth of the aspen and pine layers in the Danish peats as compared with the post-glacial oak and birch layers does answer very well to the American estimates of one and one-half to two times the duration of post-glacial time—let us take about 15,000 years. We may next compare the proteroglacial fjords with the epiglacial lakes