NORTH SYDNEY A\D SYDNEY MIXES, C. B. — DeWOLFE. 813 



uniform in their nature and arrangement than either above or 

 below. Sandstone shades off laterally and vertically into 

 arenaceous and argillaceous shales, and vice versa. These 

 horizons then must represent a comparatively prolonged period 

 of rest, during which the debris arranged itself according to 

 coarseness — the coarser sand being deposited nearest shore, 

 while finer and finer material was laid down as depth increased, 

 until at last only the finest clay was deposited. As this went on, 

 the cliflEs wore back until they were so far from the earlier shore 

 that the coarsest sand did not reach that water at all. Then only 

 the finer sand, and at length clay, spread over the original 

 coarse sand. This would produce a gradual change from coarse 

 to fine material both seawurd and upward, so that now sand- 

 stones and shales of all varjnng textures merge into each other. 



Tracing the strata upward through three feet of shale and 

 two feet of lime, another layer of shale follows containing erect 

 Calamites. Nearl}' all the shale here and for a long distance 

 above, is argillaceous. Changes usually take place suddenly 

 from coarse sandstone to fine clay without the intermediate 

 stao"es that one might expect. Next above the shale with 

 Calamites, in addition to two thin bands of limestone, are twenty 

 feet of blue gritty sandstone, very much cracked. Since there 

 are no faults or folds here, or any other structure different 

 from that of the preceding beds, it is possible that this sand 

 owing to some peculiar conditions held more water at the time 

 of deposition than the other beds. Later, the drying of the 

 stone caused shrinkage cracks producing the effect now visible. 



The next sixty feet of strata present evidence of deposition 

 on a more uneven bottom or in the presence of more erratic cur- 

 rents than any other part of the whole field under discussion. 

 Shales have been cut away and filled with sand, in a remarkable 

 manner. 



Proceeding to the next overlying strata, several small seams 

 of coal are found distribute! as in tabular section on pages 304 

 and 309. The sandstone overly ing the sixteen-inch seam is a good 



