PART 11. CHAPTER XV. 



195 



Chalk Needles Cretaceous Group. 



away the stone, as well as to throw up a beach at the same 

 level.* 



The needles of the Isle of Wight, and the Old Harry Rocks 

 of the coast of Dorsetshire, are well known to those who have 

 examined the chalk cliffs of the South of England. Besides the 

 inland columns in Normandy, above described, there are others 

 more recently formed on the sea coast of that same country. 



Fig. 171. 



JVeedle and Arch of Etretat, in the chalk cliffs of JVonnandy, 

 Height of Arch 100 feet. (Passy.)t 



If we inquire at what period the emergence and denudation 

 of the cretaceous rocks took place, we shall find that it occurred 

 in great part after the deposition of various marine tertiary forma- 

 tions, so that both the cretaceous and tertiary beds were upraised 

 together. The greatest elevation which the chalk reaches in 

 England, is the summit of Inkpen Beacon, in Berkshire, which 

 is 1011 feet above the sea; but marine deposits of the same age 

 attain an elevation of 8000 feet in the Alps and Pyrenees. 

 These may have partly emerged during the cretaceous period, 

 just as the coral reefs in some regions of the Pacific are grow- 

 ing in one spot, while other portions of the same have been 

 uplifted by subterranean forces, and converted into land. 



Difference between the chalk of the north and south of 

 Europe. — By the aid of the three tests of relative age, namely, 

 superposition, mineral character, and fossils, the geologist has 

 been enabled to refer to the same cretaceous period certain rocks 

 in the north and south of Europe, which differ greatly both in 

 their fossil contents, and in their mineral composition and struc- 

 ture. 



If we attempt to trace the cretaceous deposits from England 



* Captain Bayfield, Geol. Trans., Second Series, vol. v. p. 94. Also Principles 

 • of Geology, Index, " Niapisca island." 



t Seirie-Inferieurc, j). 142. and plate 6. fig. 1. 



