WOOD AND ROME — LIiXCOLNSHIKE AND 8.E. YOKKSHIRE. 167 



and other parts of the east of England ; and although in the imme- 

 diate neighbourhood of its origin, the Lincolnshire Wold, it seems 

 to overlie *, and towards the Wold a little to overlap, the clay 

 which is identical with the wide-spread Glacial clay of eastern and 

 east-central England, yet we conceive that as the debris of which 

 it is composed was carried further out, it became intermingled with, 

 and undistinguishable from, the general deposit of that j^art of the 

 Upper Glacial sea, its excessive chalkiness diminishing as the distance 

 from the Wold increased. At one place, South Willingham, this 

 excessively chalky clay a! is underlain by a gravel-bed, but one of 

 very limited extent, scarcely a square mile in area. This gravel 

 does not seem to us to have any connexion with the Middle Glacial 

 gravel of the east of England. 



The formation of this clay appears to us to have arisen from the 

 immense volumes of degraded chalk which were produced and pro- 

 truded into the sea by the action of a continuous or capping glacier 

 enveloping the higher elevations of the Wolds f. The nature and 

 appearance of such a glacier is described to us, in the case of that 

 at Cape York, by Dr. Sutherland, in the 9th volume of the Society's 

 Journal, who says that the surface of the land around Baffin's Bay, 

 both high and low, is now enveloped by a mass of ice which is con- 

 stantly in motion towards the sea. It seems to us that when 

 the Glacial sea first entered the depression crossed by fig. 6, the 

 supply of chalk was less, and was intermingled with material 

 brought from other parts, by which the ordinary lead- coloured clay 

 with abundant chalk resulted ; but as the cold increased, and the gla- 

 ciers gathered thicker and became continuous, the chalk debris in- 

 creased until almost the entire sediment of this region consisted of 

 it J. As we find this chalky clay passing over part of the chalk of 

 the Wold, it is clear that some elevations higher than the parts 

 where it now occurs existed, whence a supply of the material can 

 have proceeded. These greater elevations, we may infer, were 

 those lofty summits which now rise in the north-western part of 

 the Yorkshire portion of the Wold to elevations of 800 feet. So 



* No doubt is entertained by the first-named of us that this white clay of 

 Lincolnshire is the same as a precisely similar deposit worked (like this) for 

 hme, at Hedon in Norfolk, and brought first to his notice by Mr. Harmer, 

 of Norwich ; it is seen in a section in that neighbourhood to rest on an eroded 

 surface of the ordinary Upper Glacial clay of that county. This deposit, 

 so resting on the Upper Glacial clay, is undistinguishable, except by position, 

 from the chalky marl underlying the Upper Glacial clay, into which the Cromer 

 coast- (or Lower Glacial) beds pass in their western direction inland. 



t The very loftiest eminences of the Hertfordshire chalk, such as those near 

 Ivinghoe, may have, similarly to the Wolds, been sources of supply to the 

 chalky Glacial clay that occupies the lower elevations of those parts, and given 

 rise to the greater chalkiness of the clay over some parts of Herts and borders 

 of Essex, although the nodules of chalk in this are from the hard Yorkshire part 

 of that formation. 



I The anomalous case of this extensive deposit of chalky clay being quite 

 destitute of any but derivative organic remains may, pei'haps, have been due to 

 the poisoning of the water with this excessive chalky sediment, since we see that 

 the purple clay is not so destitute of organic remains. 



