270 C. A. SUSSMILCH AND T. W. E. DAVID. 



embedded pebbles ranging up to two feet in diameter ; in 

 some parts the pebbles are abundant, while in other parts 

 not far away they may be comparatively few and far 

 between. Striated boulders (always quartzites) are fairly 

 abundant in this bed. The same variety of rocks occurs 

 here as are found in the No. 1 bed. The No. 4 and No. 5 

 tillite beds do not make good outcrops, but are similar to 

 No. 3 in general character, 



The Varve Shales. — These resemble in every detail the 

 Pleistocene glacial muds from U.S.A. described by R. W. 

 Sayles 1 and the banded rocks described by the same writer 

 from the Squantum Beds near Boston, U.S.A. A detailed 

 measured section of the lower series of varve shales at 

 Seaham is shown in Fig. 1, and if this section is compared 

 with those given by Sayles in his paper a striking resem- 

 blance will be at once apparent. The varve shales at Sea- 

 ham consist of a regular alternation of relatively coarse 

 and fine layers of material; the coarse layers are yellow to 

 brown in colour, and are coarse enough for the constituent 

 particles to be visible to the unaided eye, the fine layers 

 are grey to white in colour and even under the microscope 

 the material is too fine-grained for identification. The 

 coarser layers frequently exhibit minute false bedding and 

 merge upwards into the finer layer, but the junction 

 between a fine layer with the next coarse layer above is 

 usually quite sharp. There is no doubt in the writer's 

 mind that these alternating layers represent, as Sayles 

 suggests, seasonal deposition of glacial material in a lake, 

 the coarse material representing the summer deposit 

 when the rivers draining from the glaciers were transport- 

 ing relatively coarse material; the fine layers representing 

 the fine material in suspension in the lake waters which 



1 Seasonal Deposition in Aqueo-Glacial Deposits by Robt. W. Sayles. 

 Memoirs of the Museum of Comparative Zoology at Harvard College, 

 February, 1919. 



