48 The Siskiyou Island. 



regains its normal relations to the wider out- 

 line of the continent and passes on as the 

 Cowlitz valley. Here at the head of this val- 

 ley occurs another short break in an old 

 Eocene mass, and then the trough falls into 

 line again in the depression of Puget sound. 

 A fainter continuance of this trough may be 

 traced northward through Queen Charlotte's 

 sound and even farther on. 



The geographical extent of these changes, 

 together with an approximate parallelism of 

 the working forces that produced them, 

 would seem to indicate a world wide cause 

 modified along the" Pacific slope by the coast 

 conditions, but unquestionably originating 

 from a continued shrinkage of the crust of the 

 earth. The earliest yielding to the force pro- 

 duced the Rocky mountains, the next the 

 Cascades, and the latest the Coast range. 

 These were so many upfolds of the shrinking 

 crust, each with its correlated troughs or 

 downfolds resembling the shrinkage on the 

 surface of a last year's apple. 



