194 



LYELL'S ELEMENTS OF GEOLOGY. 



Chalk Needles. 



the sea. To the same action we may ascribe the escarpments, 

 as they are called, or those long lines of precipitous cliffs in 

 which the chalk often terminates abruptly, and which, though 

 now inland, have been undermined by the waves when the chalk 

 was upheaved from the sea. 



Many examples occur in England ; but there are no precipices 

 of chalk more striking than those which bound the lower part 

 of the great valley or gorge through which the Seine flows in 

 Normandy, At various heights on the steep sides of these hills 

 are outstanding pillars and pinnacles of a very hard and com- 

 pact chalk, as at Tournedos and Elbeuf, near Rouen, which evi- 

 dently owe their shape to the power of the waves. (See Figures.) 



Fig. 168. 



Fig. 169. 



Tournedos, above Rouen. 



Fig. 170. 



Elbeuf. Elbeuf. 



Needles and grooved pillars of chalk. 



Some small columns near Elbeuf exhibit parallel and horizontal 

 grooves scooped out of the columns at different heights. (See 

 Fig. 170.) These greatly resemble certain limestone pillars, 

 described by Captain Bayfield, in the Mingan islands in the gulf 

 of St. Lawrence. There is evidence there of the coast having 

 been upheaved at successive periods, so that parallel ranges of 

 sea beaches, with recent shells, have been laid dry, terrace 

 above terrace. At heights corresponding to the beaches the iso- 

 lated masses of calcareous rock retain the marks worn by the 

 waves. These marks probably indicate pauses in the upheaving 

 process, during which the sea had a considerable time to wear 



