114 Sheppard : The Making of East Yorkshire. 



been some disturbing- element in the earth's crust which has 

 interfered all along with the regular deposition of the strata. 

 At Market Weighton there is evidence of a gradual lifting of 

 the earth's crust during this long secondary period, resulting in 

 only thin representatives of the rocks being formed. But the 

 Market Weighton unconformity is a subject sufficient for a paper 

 in itself, and beyond reference to it must not be entered into 

 now. Suffice it to say that even in East Yorkshire, simple as 

 the geology is, it has many features which indicate that every- 

 thing has not in past times run along so smoothly as one might 

 at first have assumed. 



Leaving the Oolitic rocks, with their corals and shore 

 deposits, and shallow water formations, we are suddenly con- 

 fronted with evidences of a change of a somewhat drastic 

 character. The country, in common with the greater part of 

 Europe, seems to have suffered a depression ; it was under water 

 to a great depth, and slowly but surely was covered over, as with 

 snow, by a white, soft sediment, now known as chalk. 



In the North of Ireland, in Scotland, and on the Continent, 

 as in the South and East of England, traces of this chalk sea 

 still remain. In some cases hundreds of feet of it have been 

 preserved for our study, but over large areas every trace of the 

 chalk seems to have been swept from the face of the land. 

 Mr. Lamplugh, of Bridlington, has estimated the thickness of the 

 Yorkshire chalk to be 1,270 feet, every particle of which has 

 accumulated slowly on the floor of a vast ocean, and represents 

 the dead shells or skeletons of foraminifera once living in that 

 cretaceous sea. As is the rule in geology, an idea of the nature 

 of the chalk sea is obtained from examining in detail the deposits 

 now being formed in somewhat similar situations. The 

 Challenger and other expeditions have revealed the nature 

 of our modern ocean floors. There, accumulating, is a soft 

 white substance, amongst which are teeth and bones of 

 fishes, the shells of mollusca, and other organic remains. On 

 examining the white substance under a powerful glass, it is 

 found to consist almost entirely of foraminifera, principally of 

 the kind known as Globigerina. 



On taking a piece of chalk from Hessle or Flamborough and, 

 after preparation, placing it under a microscope, it is found to 

 consist of precisely similar organic remains ; in fact, it would 

 be difficult for a novice to detect which were chalk and which 

 modern Globigerina ooze. Look into a chalk quarry, or at the 

 face of the Flamborough cliff's : in addition to the chalk proper, 



Naturalist, 



