218 ME. S. H. WAKEEN OIS" A LATE GLACIAL ^June I912, 



character, I found, early in January 1912 (the week before the 

 reading of this paper), a very remarkable bed of moss. This bed 

 extended for 6 yards along the section, and the moss was found 

 through a vertical thickness of 7 inches. 



A sample of this material was examined by Mr. H. IST. Dixon, 

 who reported that it was almost homogeneous, the mass of it being 

 composed of Hyp^ium exannulatum var. ortliophyllum (Milde), with 

 only a small admixture of H. giganteum. Mr. Dixon further said 

 that he had only once seen a fossil moss in better preservation, 

 and that was in a much more recent deposit from the Pens. 



This is the only instance so far obtained of any plant actually 

 growing upon the site. There can be no doubt that the moss grew 

 up through the silt as this accumulated. Thus the rate of accumu- 

 lation of the unstratified silt must have been sufficiently slow to 

 allow the growth of the moss to keep pace Avith it for a certain 

 length of time. This shows that the deposit was not all formed in 

 the same manner, as, indeed, one would expect from its extremely 

 variable character. 



III. The Climatic Evidence fuenished by the Aectic Bed. 



Mr. T. I. Pocock ^ has observed that the contorted ' Trail ' passes 

 imperceptibly into the gravel of Low-Level River Drift (the ' fourth 

 terrace ' of Messrs. Hinton & Kennard ^). N'ow the Trail has been 

 frequently referred, and I think correctly referred, to some form of 

 glacial action. In the Ponder's End bed there is positive evidence 

 of an Arctic climate during the deposition of this same stage of the 

 Eiver Drift. 



The climatic evidence of this bed is not essentially new. It 

 has previously been foreshadowed by the plant-bed at the 

 Admiralty Buildings, Westminster,^ and also by the work of 

 Mr. M. A. C, Hinton, on the smaller mammalia.^ At the same 

 time, the evidence from Ponder's End is more complete than any 

 that has been previously forthcoming. It is, moreover, seen in 

 two open sections, both of wide extent, and can be visited and re- 

 visited and large collections made ; while the organic remains 

 which it contains are abundant, varied, and in good condition for 

 determination. 



By collating the evidence detailed in the reports which are 

 appended to this paper, we shall note that the climatic conditions 



1 ' Summary of Progress of the Geological Survey of the U. K. for 1 902- 

 1903 ' p. 205 ; see also A. L. Leacb, Proc. Geol. Assoc, vol. xix (1905-1906) 

 p. 140. 



2 pi-oc. Geol. Assoc, vol. xix (1905-1906) p. 84. 



3 W. J. L. Abbott, Proc. Geol. Assoc, vol. xii (1892) p. 346; and C. Eeid, 

 ' The Origin of the British Flora ' 1899, p. 54. 



^ Proc. Geol. Assoc, vol. xxi (1910) p. 489. Mr. Hinton cleBerves gi-eat 

 credit for having reached the conclusion that the Low-Level Eiver Drift was 

 deposited under cold climatic conditions, although I cannot associate myself 

 with the correlation of this stage with the major glaciation of the country. 



