VARIETIES. 345 



changes again to a distinct conglomerate of pebbles, varying in size from grains to small 

 hens' eggs. What is most remarkable respecting this conglomerate, is that most of the 

 pebbles arc composed of blue hyaline quartz ; the same pebbles that occur both in the 

 red sandrock series and the quartz rock. The dip is about 50 E. The rocks extending 

 beyond Lincoln village are generally talcose schists, associated with what appears like 

 talcose sandstones, mostly altered into schists, and dipping 50 E. Nos. ^ to jfg illustrate 

 this section in the Cabinet.* 



The quartzose breccia consists of angular fragments of granular quartz, cemented by 

 peroxyd of iron. In Massachusetts this variety occurs in large bowlders six or eight 

 feet in diameter, in Great Bfirrington and Sheffield, having a cement of quartz instead 

 of iron. We have seen it also in Vermont, particularly upon the first and second 

 sections. We are quite sure that it occurs further north, but are unable to specify 

 localities. Wherever it is abundant, it may be a profitable source for iron ore. 



The coarse conglomerates are much more common, and are very interesting. They 

 consist of a paste of quartz and mica, in which are imbedded numerous distinctly rounded 

 pebbles of granular or hyaline quartz (No. ^ in the Cabinet.) The pebbles vary in size 

 from grains of sand to a foot in diameter. The situation of this deposit is invariably at 

 the east side of the formation, and generally at its base, so far as we can judge. At every 

 locality there is some variation in its character ; hence we will describe the localities. 



First, at Clarksburgh, Mass., two miles south of the Vermont line there is a deposit of 

 conglomerate from which bowlders in western Mass, have been derived in great numbers, 

 corresponding with the general description of the conglomerate. None of the pebbles are 

 larger than hens' eggs. Specimen in the Cabinet No. ^. 



At Sunderland in Vermont the largest pebbles are about the size of small beans. 

 About half of them are composed of a beautiful blue hyaline quartz : the others are of a 

 dull gray color. The contrast heightens the beauty of the specimens, and we think that 

 when polished the rock might be useful for ornamental purposes. The locality is upon 

 the hill at the eastern border of the formation on the Stratton turnpike (No. ^.) 



In Dorset and further north, bowlders of a similar conglomerate with large pebbles of 

 the same blue quartz are common. We have not found it in situ ; but the original 

 ledge must be a few miles north of East Wallingford. 



Upon the land of Nathan J. Smith, of Clarendon, in East Wallingford, about three- 

 fourths of a mile north of David Hager's, is the finest locality of this pudding stone that 

 we have seen. The out crop is half a mile long and twenty rods wide, running north and 

 south dipping 70 W. Hence the thickness of the conglomerate is at least 200 feet. The 

 conglomerate is composed of a paste of talcose matter or sandstone in which there are 

 many crystals of feldspar, containing the large and small pebbles imbedded in it. The 

 pebbles are mostly of an oval shape, having the longer diameter coinciding with the line 

 of strike. Others are drawn out at great length, by a process explained in our First 

 Part (specimens in the Cabinet Nos. jy to jj.) 



The conglomerate is interstratified with cuneiform-shaped beds of talcose schist, both 

 varieties insensibly passing into each other. This schist differs but little from the so called 



* The rocks east of the fault are now considered as forming a distinct group of strata, and are elsewhere described as talcose 

 conglomerates. 



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