Mathematical and Physical Papers. 249 



out to us how the waters in the upper levels to the north and west 

 of us get down from the Columbia river level, fifty feet above the 

 first sand level, to the lower sand level. In making the railroad 

 cut just north of Mount Vernon a fault in the Columbian blue-clay 

 base is shown for over 100 feet in length. The blue clay shows a 

 continuous line for a long distance, but quite suddenly a fault is 

 disclosed, the clay capping over a sand bed for some twenty feet ; 

 then a clear sand bed occurs for eighty feet. This would, of course, 

 allow the water on the upper level to go through. As a matter of 

 fact, this river-bed is now dry, whereas four miles back it carries 

 the water." 



