Position of the Strata. 221 



the breadth of this formation increases, we find the dip to decrease ; 

 so as in many places to be almost nothing. 



As to the thickness of the formation under consideration, we have 

 not sufficient data for forming a very definite opinion. Perhaps, 

 however, we may obtain a proximate estimate, by examining an east 

 and west section of the formation, across the south part of Deerfield 

 mountain, and the center of Mount Toby. The following sketch is 

 not intended to be precisely accurate ; but only to give a general idea 

 of the relative situation of the two mountains and the intervening val- 

 ley, with the valleys between them and the primary rocks on the east 

 and west. There must always be, as is well known, more or less of 

 distortion and want of proportion in sections of this kind, where the 

 horizontal scale must be much smaller than the perpendicular one. 



In the present case, in order to exhibit the proper dip of the strata, 

 the valley through which the Connecticut flows, is represented too 

 wide. 



It will be seen by this section,* that the strata, both in Deerfield 

 mountain and Mount Toby, as well as in the valleys, have the medi- 

 um easterly dip of the formation ; that is about 15°, though on a con- 

 siderable part of Mount Toby it is hardly 10°. Two or three hun- 

 dred feet above the river, on the east side, may be seen a mass of 

 greenstone ; which, so far as I can ascertain, constitutes a dyke or bed 



* This section (when it was too late to have it corrected,) was found to be very 

 badly engraved. The dotted lines crossing- the valley, should correspond with the 

 strata on the two mountains ; and the dip of the lower beds should be several de- 

 grees larger. 



