THE LAST DECADE. 
409 
as chalk. The fossils which are found in chalk are indicative of 
animal life existing in shallow water. The chalk in Yorkshire is 
characterised by different forms of flint, which, in the several beds, 
maintain a characteristic appearance. The uppermost beds are 
devoid of flint, but on analysis the chalk is found to yield twice as 
much silicia distributed throughout its mass as the chalk which con- 
tains flint nodules. During 1885 the same author contributed papers 
describing some sections formed during the construction of the Hull 
and Barnsley Railway at Gave and Drewton, and the physical geo- 
graphy of the East Riding of the county. He also described a 
series of parallel roads in Gleugloy, of similar structure to those of 
the far-famed Glenroy. In 1887 Mr. Cole contributed a paper on the dry 
valleys in the chalk ; during the month of January, a succession of 
frosts had frozen the bare ground so hard that no rain could penetrate, 
but was quickly converted into ice. Snow also fell, and w^as repeat- 
edly melted and re-frozen. The snow and ice gradually descended 
and accumulated in the bottom of the valleys. On a sudden a rapid 
thaw ensued, and in a few hours the dale bottoms were converted 
into roaring torrents, in some cases three feet deep. The gTound 
was still frozen hard underneath, su that the water could not penetrate. 
Large quantities of loose chalk and rubbish were carried considerable 
distances and re-deposited further down the valleys. The author 
referred to a paper by Mr. Clement Reid, read at the Geological 
Society of London, on the origin of dry chalk valleys, in which he 
showed that with a frozen sub-soil the drainage system of the chalk 
might be entirely modified and the underground circulation stopped. 
Mr. Cole recorded the above instance as affording some confirmation 
to this view. 
In 1881 Mr. J. R. Mortimer described a series of sections in the 
drift obtained whilst forming the new drainage works at Driflield. 
They were cut in the purple clay and Hessle clay, frequently intri- 
cately dove-tailed and squeezed together so as to obliterate every 
well-marked line of separation, intermixed with patches of chalk 
gravel, and sand. These j\Ir. Mortimer attempted to correlate with 
more extensive deposits throughout Holderness. In 1886 Mr. 
Mortimer also described a series of lauce-pointed terraces or plat- 
