178 Scientific Geology. 



unless they constituted an ocean deep enough to cover the whole sur- 

 face of the State. And such a submersion is rendered improbable by 

 the horizontal position of the layers of clay ; which shows that no 

 elevating force has acted upon the State since their deposition. Their 

 production in different and independent basins of water, such ponds, 

 perhaps, as now exist in Middleborough, Troy, Falmouth, Webster, 

 &c.* is the more probable hypothesis. 



I call these various deposites the newest tertiary in the State. 

 But my only proof that they are newer than the plastic clay of the 

 southeast part of the State is, that the strata of the latter, at least, at 

 Martha's Vineyard, are inclined at a high angle ; while those of the 

 former are horizontal. And we know that the older strata are gen- 

 erally, though not always, more inclined than the newer. I know of 

 no place where these two series of strata are in contact, so that their 

 true relative position may be seen. 



Mineral Contents. 



I place in this formation the extensive beds of the hydrate of iron, 

 (Limonite, Beudant: Prismatic Iron Ore, Mohs: Brown Oxide of 

 Iron, Cleaveland,) which occur in the limestone valleys of Berkshire 

 county : and in connection with the same range of limestone and 

 mica slate, in Vermont and Connecticut. I am aware that in doing 

 this, I deviate from the opinion of several geologists, who have ex- 

 amined these beds, and seem inclined to regard them as belonging 

 to the mica slate or gneiss.f But I could not find the slightest evi- 

 dence, at any bed of this ore which I visited, that it is interposed be- 

 tween layers of mica slate, gneiss, or any other solid rock. It is, 

 however, usually associated with more or less of clay ; and, there- 

 fore, I regard it as belonging to a tertiary formation. Generally, the 

 bed is covered by nothing but diluvium; and diluvial action seems 

 sometimes to have disturbed the ore to a considerable depth, so that 

 my doubt has been, whether it ought not to be placed even as high as 

 diluvium, rather than whether it belongs to the primitive rocks. Pro- 

 fessor Silliman does, indeed, speak of a ledge of gneiss, as being 

 brought to view by the excavation at Kent, in Connecticut, in the 



* The name of the principal pond in this latter place, although not given on the 

 map, deserves to be mentioned, because it is so laconical and euphonical. It is 

 Chargoggagoggmanchoggagogg. 



t Am. Journal of Science, Vol. 2. pp. 213 and 216 : also Vol. 8. p. 30. 



