50 The Siskiyou Island. 



are describing, but was pierced by straits 

 through which the ocean freely flowed till it 

 washed the slopes of the Cascade hills. This 

 free inflow of the ocean kept the enclosed body 

 of water salt enough to promote the health 

 and abundance of its sea shells, and no region 

 of Miocene times has kept a fuller record of 

 its life. And if now we are led to ask where 

 the Miocene agencies found the materials for 

 these later upbuildings of hills, we may re- 

 member that the great upfold we now call 

 the Coast range, once in place, settled into 

 two sorts of materials, a denser, heavier por- 

 tion that formed the mud-sills, and a lighter 

 topping lifted skyward. It was the work of 

 Miocene weather wear to form the skyward 

 portion into graceful drapery for our coming 

 valley. In short, Miocene winds and rain 

 transported these looser Miocene materials 

 into gentle inland slopes, to be in time cov- 

 ered by the tides of the ocean and stocked 

 with sea shells until it became a grand Mio- 

 cene aquarium. 



