Consolidated Diluvium. 



151 



ique and interesting example of diluvium. It lies on the eastern 

 side of Hoosac river, against a hill of mica slate ; and rises, at least, 

 100 feet. It consists of pebbles of quartz and micaceous and argil- 

 laceous slates, from 8 or 4 inches diameter, down to coarse sand: and 

 a part of the mass is consolidated into conglomerate and sandstone. 

 (Nos.25, 26,27, and 28.) The cement is carbonate of lime ; which hav- 

 ing been dissolved in water, has been diffused uniformly through the 

 mass. It is not perceived by the eye ; but on applying acid, a brisk 

 efferescence ensues ; and hence I infer that it was infiltrated in a state 

 of solution. And although I could perceive but few fragments of 

 limestone among the diluvium, yet as the whole region abounds in 

 this rock, it is hardly possible that it should not exist there, at least, in 

 the state of sand. This being admitted, the consolidation of this 

 stratum is easily explained by causes now in action ; and a question 

 might be raised, whether diluvium consolidated in this manner, does 

 not in fact become alluvium. I ought to add, that when thus forming 

 solid masses, it is as distinctly stratified as are most of our secondary 

 sandstones and conglomerates. 



How common may be consolidated diluvium, in this country, I 

 cannot say. But I believe no account of any other locality has been 

 published. In Europe, geologists describe a similar rock, if Bron- 

 gniart's Terrains Clysmiens, is synonomous with diluvium : for he 

 says that "the parts of the rocks of that class are sometimes united 

 by a base or cement chemically produced; that is, by solution."* 

 At any rate, the consolidated shingle bed, described by Mr. Mantel! 

 in his Geology of Sessex, as occurring at Brighton, in England, 

 must be regarded as of the same character as that in Pownall above 

 described. 



The diluvial deposites in Massachusetts, whose topography I have 

 now described, were probably produced originally, by all the abrad- 

 ing and disintegrating agents that were in operation on the surface of 

 the globe, between the time when the solid rocks were deposited, and 

 the last deluge. These agents, so far as we know, were the same as 

 are now operating to modify the earth's surface ; and have been des- 

 cribed under alluvium. Hence there must be great diversity as to- 

 the times when the different portions of this diluvium w r ere produced. 

 But I maintain that all of it has been subject to the modifying influ- 

 ence of, at least, one general deluge of waters in more recent times. 



* Tableau des Terrains, p. 66. 



