68 Royal Society, 



will need many years of careful observation before sufficient data can 

 be obtained for accurate calculation. 



1st. With the high-level gravels there are connected a number of 

 sand and gravel pipes, perforating the underlying chalk to the depths 

 generally of from 5 to 50 feet, and from 1 to 10 feet wide, or more. 

 As these are caused by the slow action of carbonic acid in the water 

 gradually percolating through the overlying porous beds, dissolving 

 the chalk or other calcareous strata, and gradually letting down the 

 superincumbent drift, it is evident that, if the rate of solution and 

 removal can be determined, one element for the calculation of a cer- 

 tain period will be obtained. In this, various meteorological questions 

 will have to be considered. 



2nd. In conducting observations on the temperature of deep mines, 

 wells, &c., certain discrepancies in the increment of heat at increas- 

 ing depths and at diiferent places have been noticed. No explana- 

 tion of these anomalies has been offered. The author suggests that 

 they may arise from disturbing causes originating with a former 

 period of intense cold. At Yakutsk, where the ground is now frozen 

 to a depth of 382 feet, the permanent line of 53° Fahr. would, taking 

 at an average an increase of 1° for every 60 feet, be found at a depth 

 of 1642 feet. If, from some geological change, the mean tempera- 

 ture of Yakutsk were raised to that of our own climate, this line of 

 53° would undergo a vertical displacement of 1550 feet. The time 

 required for its uniform re-adjustment over a large area would depend 

 upon various conditions, the chief one being the conductivity of the 

 different strata. The question, therefore, arises, whether traces of 

 perturbation in the temperature of the outer part of the earth's crust 

 in these latitudes, resulting from the action of the extreme cold of the 

 glacial period, may not yet exist, and, if so, whether they may not 

 admit of exact determination with reference to the time elapsed since 

 the removal of the disturbing cause. 



In conclusion, the author thinks that in the present state of the 

 inquiry it would be premature to attempt to fix even approximately 

 the lapse of time attaching to the flint-implements. It is obvious, 

 however, that our present chronology with respect to the first appear- 

 ance of Man must be very greatly extended ; but, like a mountain- 

 chain in the distance, its vast magnitude is felt before an exact 

 measurement of its height and size can be taken. 



Attention is then directed to the remarkable uninterrupted succes- 

 sion of life from the pleistocene period under review to the present 

 time — a succession so large and important, that it is not possible to 

 imagine the occurrence of any intervening catastrophe of such a 

 nature as to destroy the life of the period over this part of Europe at 

 any recent geological period. There are difficulties in the problem, 

 especially the disappearance of the larger animals ; but the remark- 

 able and convincing feature in the case is the transmission to our 

 time of so large a proportion of the small and delicate land and 

 freshwater shells, which even now follow almost precisely the same 

 law in their distribution as they did at these latest geological periods. 



Looking at the special nature of the glacial period, and seeing its 



