40 Reports and Proceedings. 



2. *' On tlie relation of the Bonlder-clay without Chalk, of the 

 North of England, to the Great Chalky Boidder-clay of the South." 

 By Searles V. Wood, jun., Esq., F.G.S. 



The author described the Yorkshire Glacial clays as of two kinds — 

 the lower, containing chalk debris, and belonging to the uppermost 

 member of the Glacial series in Eastern and East-central England ; 

 the upper containing chalk sparingly in its lower part, and gradually 

 losing this upwards. On the coast the latter occurs only north of 

 Mambro'. He stated that, Palaeontologicall^r, the lower and middle 

 Glacial deposits closely agree with the Crag, and are quite distinct 

 from the deposit at Bridlington, which he placed immediately above 

 the "Great Chalky Clay." 



The absence of chalk debris in the deposit north of Flambro' has- 

 been regarded as evidence of a drift from north to south ; but the 

 author stated that the purple clay without chalk extends over much 

 of the north-eastern part of the Wolds, from the sea-level to an 

 elevation of 450 feet, and that outlines of it occur at intervals along- 

 the Holderness coast-section as far as Dimlington, 42 miles south of 

 the northern limit of the Wolds. In the direction of Flambro' and 

 York the clay was said to be destitute of chalk, which would not be 

 the case had the Wolds fonned a sea-shore, causing a drift from the 

 north to pass either to south-east or south-west. 



The author described the characters of the Great Chalky Boulder- 

 clay in the Eastern and Central counties of England, and maintained 

 that the chalk found in it (eqi;al, according to him, to a layer of at 

 least 200 feet over the entire Wold) could only have been detached 

 by the agency of moving ice, which he believed to have covered 

 nearly the wliole Wold for a long period. 



The author stated that Boulders of Shap Fell granite are confined 

 to the deposit of clay mthout chalk, and discussed the means by 

 which they could have been distributed. He ascribed their dispersion 

 to the agency of floating ice during an adequate submergence of the 

 district. He supposed them to have passed from Shap Fell by what 

 is now the j)ass of Stainmoor. 



Thus he ascribed the formation of the " Great Chalky Clay" ta 

 the extrusion from the sea-foot of a great sheet of ice, of materials- 

 abraded by the latter, the land being depressed 600-700 feet below 

 its present level ; and that of the clay without chalk, and with 

 Boulders of Shap Fell granite, to deposition dm-ing a peiiod of much 

 greater dej^ression (about 1,500 feet), throughout which the sea bor& 

 much floating ice. He considered that the " Great Chalky Clay" 

 indicated a long period, during which the land, with its enveloping- 

 ice, remained stationary, and that during this period, when intense 

 cold prevailed, the Arctic fauna of Bridlington became established. 

 He thought that the recommencement of subsidence was indicated 

 by the reddish-brown or brownish-purple sediments of Holderness, 

 in which some chalk occurs. He then indicated the species of 

 Mollusca which have occurred in the purple clay without chalk 

 about Scarbro' and Whitby, all of which were said to belong to 

 existing forms, and thus to be in accordance with the date assigned 



