72 



R. S. TARR 



Beneath this clay layer, in every well of which there is a 

 record, a series of coarser beds is found. These coarse beds vary 

 greatly even in neighboring wells ; but in most cases there are 

 both sand and gravel layers. The bottom of the series of coarse 

 sediments varies from 6o to approximately 120 feet, and the 

 thickness in individual wells from 20 to about 70 feet. The 

 coarser sands are clear and well washed ; the gravels consist of 

 well-rounded pebbles similar to those now brought down by the 

 torrential creeks that enter the valley. 



In most of the samples preserved from these coarse layers 

 plant fragments and moUusca were found. Seven logs were 

 encountered, and the two logs found in the overlying clays were 

 almost down to the level of the coarser series. Thus between 

 the depth of 35 and 119 feet nine logs were encountered in 

 boring thirteen six-inch wells. Since two of the wells passed 

 through two logs each, logs were encountered in seven out of 

 thirteen wells. The depth of the several logs is given in the 

 following table : 



In all the deep wells the coarser layers are underlain by a 

 great thickness of clay, in which no molluscan remains were 

 found, though in several samples small, indefinite plant fragments 

 occur. In most of the wells the driller failed to preserve more 

 than one sample, which he considered typical of the entire clay 

 mass ; but near the top and bottom of the series the material is 

 occasionally reported as "clay and stone," "clay and gravel," 

 or "clay and sand." In one well (the south well), however, 

 samples were preserved every ten feet, and these samples show 

 clearly the nature of the material. From top to bottom, that 



