176 



Scientific Geology. 



hill a mile south of Brattleborough east village,) it falls but little short 

 of 10°. A less dip may be seen in the clay hill east of Deerfield 

 Academy : and in the east part of Hadley, on the middle road to 

 Amherst, the laminae conform to the gentle swells and depressions of 

 the ground. At the base of steep hills, however, the clay beds are 

 generally horizontal ; because, as I suppose, the declivity was too 

 steep to permit of these depositions in a conformable manner. This 

 fact, and the circumstance that in those cases where there is a slight 

 inclination of the clay bed, the dip follows no general law, but con- 

 forms to the surface, has led me to conclude that this tertiary forma- 

 tion remains as it was originally deposited. I mean that the few 

 cases of dip which exist, do not prove any disturbing force acting 

 subsequently to the deposition of the formation. And I think we have 

 in these cases, the maximum of inclination in a sedimentary deposite 

 of clay and sand, formed in still water. For since hills of every de- 

 gree* of inclination mast have existed in the bottom of lakes, ponds, or 

 the ocean, in which this formation was deposited, the layers of sand 

 and gravel would have remained in a conformable position on every 

 slope that was not so steep as to cause the materials to slide down. 

 I think that in no case the inclination is more than 10°; although I 

 have not applied the clinometer. 



The measurement of a base line for a trigonometrical survey of 

 the State, in the valley of the Connecticut, by Col. Stevens, during 

 the year 1831, has furnished another proof that this tertiary forma- 

 tion has not been disturbed since its deposition. For the tracery of 

 that line, (nearly eight miles long,) was made upon this formation ; 

 and the two extremities were found to correspond in their level with- 

 in three feet. 



Mr. Smith, in his account of the Connecticut river valley, in Vol- 

 ume 22nd of the American Journal of Science, states that the greatest 

 elevation of clay beds along Enfield Falls, is about fifty feet above 

 the present surface of the river ; and this, if I understand him, ex- 

 ceeds the general thickness of the clay beds in that region. But as 

 we descend into the basin in which the village of Deerfield is situ- 

 ated, the clay, without any alternation of sand, is exposed not less 

 than 60 feet in depth ; and still the bottom is not seen. A little east 

 of the Academy, in the same town, the layers of clay rise 30 or 40 

 feet above the plain, and at the same place have been penetrated at 

 the foot of the hill, 25 feet, without reaching the bottom : so that in 

 this valley, this single bed of clay, cannot be less than 60 or 70 feet 



