Newest Tertiary. 



173 



The most recent Tertiary. 



The most extensive deposites of the beds of this class, are in the val- 

 ley of the Connecticut ; where they are marked on the map. They 

 occur also, in small patches in many other places in the State : but 

 they have been marked on the map in no other place, except in Cam- 

 bridge and Charlestown. The great resemblance in the mineralo- 

 gical characters of these beds all over the State, their horizontal posi- 

 tion, and the almost entire absence of organic remains in them, so 

 far as they have been examined, have made it impossible to describe 

 them as distinct deposites ; though I have little doubt, that many of 

 them, at least, are such. Yet probably they do not differ much in 

 age. But I leave to future observers to settle what I have no means 

 of deciding. 



These newest tertiary strata consist of horizontal alternating layers 

 of white siliceous sand and blue plastic clay. Along the Connecti- 

 cut, the sand occupies the highest place in the series ; and covers 

 most of the surface. Its upper portion is disturbed and piled up 

 irregularly by diluvial action ; and sometimes mixed with transported 

 gravel. But where the streams have worn passages from 10 to 15 

 feet deep, they have almost uniformly disclosed the stratum of clay. 

 And not unfrequently tracts of considerable extent are entirely swept 

 of sand, whereby the soil is rendered highly argillaceous. Generally 

 the beds of sand and gravel appear to be several feet thick ; but some- 

 times I have found numerous alternations in the height of a few feet, 

 or even a few inches — some of the layers not being more than half 

 an inch thick. Some years since, I obtained the following rough 

 sketch of a cliffy a few feet in height, in Deerfield ; the face of which 

 had recently been laid bare by the sliding away of its outer portion. 

 The beds, a a, &c. b b, &c. c, and d, represent different horizontal layers 

 of sand and clay ; the former becoming often very fine, and the latter 

 sometimes approaching to loam. Some of the layers of clay were not 

 more than half an inch thick ; and these in general, with the inter- 

 stratified sand beds, appeared as if deposited from water perfectly at 

 rest. But the stratum c, presented a most remarkable exception. It 

 was composed of angular and rounded pieces of clay, mixed with 

 sand, and obviously resulted from the breaking up of several thin 

 beds of clay and sand, by some unusual agitation of the waters. 

 The stratum d, was still more remarkable. It consisted of sand and 

 two layers of clay ; the latter being very irregularly bent, as if, 



