218 GLACIAL DEPOSITS CHAP. xn. 



pliocene, or to consider them as beds of passage between the 

 newer pliocene and post-pliocene periods. The fluvio-marine 



Fig. 28 



Cyclas (Pisidium) amnica var. ? 

 The two middle figures are of the natural size. 



series usually terminates upwards in finely laminated sands 

 and clays without fossils, on which reposes the boulder clay. 



This formation, No. 4, is of very varying thickness. Its 

 glacial character is shown, not only by the absence of stratifi 

 cation, and the great size and angularity of some of the 

 included blocks of distant origin, but also by the polished 

 and scratched surfaces of such of them as are hard enough to 

 retain any markings. 



Near Cromer, blocks of granite from six to eight feet in 

 diameter have been met with, and smaller ones of sienite, 

 porphyry, and trap, besides the wreck of the London clay, 

 chalk, oolite, and lias, mixed with more ancient fossiliferous 

 rocks. Erratics of Scandinavian origin occur chiefly in the 

 lower portions of the till. I came to the conclusion in 1834, 

 that they had really come from Norway and Sweden, after 

 having in that year traced the course of a continuous stream 

 of such blocks from those countries to Denmark, and across 

 the Elbe, through Westphalia, to the borders of Holland. 

 It is not surprising that they should then reappear on our 

 eastern coast between the Tweed and the Thames, regions not 

 half so remote from parts of Norway as are many Russian 

 erratics from the sources whence they came. 



According to the observations of the Rev. J. Grunn and the 



