198 Fisher— Ages of the " Trair and " Warp." 



was one of its later phenomena, and tlie retirement of the sea, wLicli 

 deposited it, formed the commencement of the recent period. ' 



It is very satisfactory to observe that the periods thus assigned to 

 the two Grlacial phenomena, which I have been discussing, cause 

 them to fall into the positions which they ought to occupy on purely 

 geological grounds, and agree with awards of Sir Charles Lyell 

 and Mr, Prestwich. From reasons, solely gromided upon the order 

 of superposition, I concluded my paper on the warp with the following 

 summary : — 



" Upon reviewing the changes which have been indicated by the 

 phenomena discussed in the present paper, we have disclosed, in the 

 first instance, a condition of the surface when the general features of 

 the landscape were the same as at present, during which the great 

 mammalian fauna flourished contemporaneously with the fabricators 

 of the chipped flints " (the Palseolithic period). 



" We have, subsequently, though perhaps not in immediate sequence, 

 a period of extensive denudation, indicated by the furrows filled with 

 materials from the higher grounds, which have travelled in a plastic 

 state, and which I have called ' trail.' This denudation brought the 

 surface almost exactly to its present form. The period of the for- 

 mation' of the warp succeeded, in which the winter frosts seem to 

 have been more severe than at the present time. 



"■ It was either during this period or shortly afterwards, that the 

 submarine forests flourished. A submergence of moderate amount, 

 measured by a few tens of feet, next followed, and the Scrobicularm 

 mud was deposited over the lowest forest-grounds. The sea was 

 then depressed again, and the recent period commenced. 



"The changes of form in the present surface which have taken 

 place since that time may, I believe, be easily recognised, since they 

 usually interrupt the more general contour of the surface."^ 



Upon correlating these geological conclusions, with what may be 

 called our astronomical ones, we find that the Paleeolithic period, 

 shown to be older than the " trail," is thrown into the times ante- 

 cedent to Sir Charles Lyell's period a ; where, also, he himself 

 places it. Nevertheless, if I should venture to differ from so great an 

 authority, I would suggest that the period b, to which he inclines to 

 assign it, might be somewhat too early, the eccentricity being likely 

 to have rendered it too cold for the phenomena observed, and that 

 the climate of some part of the intei-val between 100,000 and 200,000 

 before a.d. 1800, would have been more in accordance with what 

 was requisite, and probably of sufiScient duration. 



There followed after the Glacial era of the " trail,'' a lengthened 

 period of equable seasons of about 80,000 years, which would have 

 been that of the submarine forests and their occupants. Elephas primi- 

 genius was still living in this Island, — witness his remains found at 

 Holyhead harbour, preserved in the British Museum. 



A short period of severe winter cold succeeded, which was the 

 period of the warp, and of the ScroUcularia clays ; and the date of 

 it agrees remarkably with the result arrived at by Mr. Prestwich, on 

 ^ Geol, Journal, vol. xxii. p. 664. ^ Ibid. 



