Postelsia 
Oo 
ie) 
= 
down. The transformation of the accumulated, 
rounded grains into a crystalline, orderly mass 
was not accomplished in one geologic epoch but 
in many. That heat could have played no un- 
usual part we do certainly know; pressure play- 
eda part, because where the topmost lamine of 
the formation had been laid upon each square 
foot of sea bottom, at Providence Cove 1,000 
tons rested, a load for a freight train of twenty 
cars. Time is represented in a series of results 
otherwise very difficult to comprehend. If frag- 
ments be broken, the ring is sharp and clear. 
The material is so clear of impurities that every 
piece is attached to its neighbor in the most 
intimate crystalline contact. 
Much variation in this crystalline condition 
cam be noted. “At Providence (Cove the rock 
seems throughly indurated. This is not due 
alone to the fact that thousands of feet more of 
sediment was laid upon it than upon the beds at 
the Station, but in part to a difference in the 
mineral and chemical composition of the sedi- 
ment itself. Here is more silica as well as more 
uniformity in composition. Under a great 
