TRANSACTIONS OF SECTION C. 617 



4. On Sections of the Drift ohtained from the new Drainage Works of 

 Driffield.^ By J. R. Mortimer. 



The plan and sections of the Driffield drains cover an area of forty acres, show- 

 ing a length of six miles. The noticeable feature is the complicated interbedding 

 of sand and gravel with boulder clay. 



The gravels consist almost entirely of waterworn pieces of chalk of small size, 

 though foreign boulders are occasionally present ; and the fact that both chalk and 

 boulders are frequently found standing on end shows that they must hare been 

 dropped into their position by ice. 



The dovetailing of the chalk gravels with the boulder clay is confined to a 

 narrow zone, bounded by the chalk hills on the one side, and on the other by a 

 series of mounds and ridges, distant from the chalk one mile at Bridlington, and 

 five at Hull. The mounds are not moraines, but due, the author thinks, to the 

 melting of stranded ice-rafts bearing sand and gravel. They exhibit every variety 

 of false bedding, due to rearrangement by tides, and are capped by an unstratified 

 boulder clay. The remarkable features shown in the sections are due to ice action 

 — the land ice bringing down fresh supplies of chalk — the sea-borne ice ploughing 

 up the clays and preventing the escape of the gravels. Many instances can be given 

 of chalk crushed and removed by ice. 



The author considers that an ice-cap covered the chalk hills, filling up the 

 Talleys, and preventing subaerial denudation, and that the drift which fills up old 

 preglacial valleys in the neighbourhood of the present coast never extended far 

 inland, as no trace of it is to be found in any of the dales. 



In tracing the position of the chalk gravel, the author calls attention to the 

 striking fact that chalk boulders south of Hornsea contain hlack flints, which are 

 never found in the Yorkshire chalk, and which must have come from Norway. 

 The flints north of Hornsea are more of the Yorkshire type, and were probably 

 derived from Flambro' Head. 



5. On the Subsidences above the Permian Limestone between Hartlepool 

 and Ripon. By A. G. Cameron, Geological Survey of England and 

 Wales. 



In this paper attention is drawn to the numerous fonns of shrinkages of the 

 land-surface, often extending to considerable depths into the rocks beneath, 

 observable over the top of the Permian rocks betwixt Hartlepool and Eipon. 



As a general explanation of their origin, it is suggested that where the under- 

 ground water, flowing over the limestone surface, reaches the margin of the sand- 

 stone, it receives a check, whereby it accumulates, forming a chain of dams or 

 pools along the line of junction of these rocks. 



As denudation proceeds, hollows form above and below, until ultimately the 

 phenomenon of the pits appears. 



This being so, ' the water bubbling and frothing all over ' is explained with- 

 out calling in the aid of river-action. 



Allusion is made to the Home Farm Colliery accident at Hamilton, N.B., in 

 February 1877, through a subsidence in the gravelly alluvium of the Clyde ; also 

 to the recent subsidences at Blackheath, near London ; and to the extensive caverns 

 in the hematite districts of Furness. 



6. The Glacial Deposits of West Cumberland . By J. D. Kendall, G.E., 



F.G.S. 

 The extent, form, and inner nature of these deposits were first described, o 

 number of new and important facts being brought forward on the distribution of 

 boulders both in the boulder clays and in other glacial deposits. 



' This paper will be printed in extenso in the Proceedings of the Yorkshire Geologi- 

 cal and Polj^echnic Society. 



