CONGLOMERATES. 175 



'cinders/ and had been erroneously supposed to be of some economical importance. Numerous irregular 

 cavities in it have a mammillary surface, and a number of small angular stones are imbedded in it, forming a 

 kind of breccia. A similar case occurs at Mallett's Bay, Colchester. At the base of a ledge of silicious 

 limestone east of Mr. Church's house in Highgate, is a very solid tufa, with the surfaces mammillary or 

 densely covered with very minute tubercular and botryoidal stalactites. In some cases, as in Derby and 

 at Mallett's Bay, the tufa contains so much gravel as to approximate to a conglomerate. 



Stalactites are common in most of the numerous caves in the Eolian limestone. Some of them are 

 immense, being three feet or more in diameter. In the caves that are most visited, the stalactites have 

 mostly been broken off by visitors. 



ALLUVIAL CONGLOMERATES. 



In Pownal, half a mile north of the State line, and upon the northeast bank of Hoosac 

 River, is an interesting example of a calcifcrous conglomerate, and sandstone. The process 

 of consolidation seems to be going on every day ; the cement being the calcareous matter 

 derived from subjacent limestones. (See <J, in Cabinet.) 



There is a similar but harder conglomerate cemented by lime, in Westford, on the land 

 of Dr. Haines. 



Similar conglomerates may be found in several places in Pittsford. 

 Other conglomerates are cemented by the hydrated peroxyd of iron. A ferruginous 

 conglomerate is described by Prof. Adams, in Warren, where it was found by Mr. William 

 13. Tyler, about two miles west of his house, having been revealed by a brook. In the 

 east part of the town we saw another example, associated with calcareous tufa. . 



So great an amount of consolidated drift was found in Shaftsbury and other towns in 

 the great Taconic valley, that we are disposed to believe that a great part of the coarser 

 deposits in the western part of the State, which are located upon highly ferruginous lime- 

 stone, will be found to be consolidated. 



There is a locality of interest, of this kind, in Dover. It is represented in Fig. 95. In 

 a ferruginous serpentine, Rock river has cut a deep gorge, C, with 

 precipitous sides. In the bottom of this gorge is a consolidated 

 conglomerate, B, as tough as new red sandstone, and containing 

 many large pebbles. The river has cut through this conglomerate 

 at A. Hence in this gorge there has been a double amount of ero- 

 sion performed. First the gorge itself was excavated from solid 

 rock. Then the gorge was filled, perhaps entirely, with coarse 

 gravel of the drift period. By the time that the ocean had retired, 

 the gravel had been cemented together by the peroxyd of iron 

 decomposing from the serpentine, so that the river must wear it away before it can resume 

 its former position. The conglomerate is now mostly worn away. 



MANGANESIAN DEPOSITS. 



"Manganese wad is found in reniform masses in a swamp in More town ; also in the east part of Brandon 

 and in Lowell, in small concretions. In some instances masses of sand are cemented by this mineral, 

 forming sandstones which are less coherent than those of calcareous or of ferruginous origin. Traces of 

 hydrate of iron are more or less distinct on the surface. In the east part of Warren, Dr. Thresher pro- 

 cured specimens, which contain a large portion of manganese. In the northeast part of Benson, there 

 is a bed of this sandstone in a hill side. In Stowe, on land of Mr J. Downer, it occurs with a firmer 

 texture." 



