164 G. Slater — Human Skeleton in Glacial Deposits. 



Derbyshire were felt "so far away as Grange and Sih'erdale ". 

 I venture to think that the presence of this dark limestone in 

 a lighter matrix may be explained in a much simpler way. 



In the Crich area we have limestone of every shade of colour from 

 white, through grey, light blue and dark blue, to black. There is 

 generally a clear line of demarcation between each shade of colour, 

 and this frequently takes the form of an impervious clay-band. The 

 mottled beds are also present, and they invariably, so far as my 

 observation goes, form passage beds between lighter and darker shades 

 of the rock in places where there are no claj'-bands to delimit the 

 areas of the two shades. These mottled beds are called ' curly ' by 

 the quarrymen, in allusion to their somewhat irregular fracture, 

 which frequently follows the boundary-lines of the dark patches, as 

 Messrs. Barnes & Holroyd state in their paper. 



In Hilt's Quarry, Crich, where the mottled beds may best be 

 studied, they occur on two horizons: (1) between beds of white and 

 light-blue limestone, (2) between beds of light-blue and dark-blue 

 limestone. In each case the two shades of the mottled or ' curly ' 

 rock are the same as those of the rock above and below respectively. 



There can therefore, I think, be no doubt that the dark and the 

 light of the mottled rock are the same limestone ; in other words, 

 that they were deposited contemporaneously. 



The varying shades of colour in the limestone are due to varying 

 proportions of carbonaceous or bituminous matter contained in it. 

 The percentage of such matter in specimens collected in Hilt's Quarry 

 ranges from 0'62 in the white to 2-02 in the black. (Analyses by 

 Mr. Eric Sinkinson.) 



The presence of- this carbonaceous or bituminous matter in the 

 limestone is difficult to explain satisfactorily in all circumstances, 

 especially in view of its frequent impersistence horizontally. The 

 matter is still under investigation, and I hope to have more to say 

 about it before long. At present it seems probable that it may be of 

 both original and secondary origin — original in regard to organisms 

 embedded during deposition, secondary as the result of subsequent 

 infiltration. Pos.«ibly the latter has had the wider effect. 



Finally, I suggest that if the supply, whatever be its source, were 

 insufficient to permeate fully the rock accessible to its influence, 

 there would be a tendencj', owing to the nature of the substance, for 

 it to collect into oleaginous patches, of shape and size varying 

 according to tlie supply available and the conditions of environment, 

 such as capillar}" influences, degree of porositj^ etc. This I believe 

 to be the explanation of the mottled or ' curly ' rock. 



Vr. — The occuekence op a Human Skeleton in Glacial Deposits 



AT Ipswich. 



By George Slater, F.G.S. 

 TMHE great interest excited by the recent announcement in the 

 JL Times and elsewhere of the alleged discoveiy of a skeleton of 

 " pre-Boulder-clay man" renders it desirable that the geological 

 evidence should be carefully examined. 



