VAEIETIES. 343 



as that of the pencil slates of Rutland County ; one homogeneous mass. It is remarkably 

 compact and enduring. Bowlders of it may be found all over the southern part of the 

 State ; even three feet in diameter fifty miles from the parent ledge. Along the range 

 of this rock these bowlders cover the surface, making tillage almost out of the question ; 

 and they have received the appropriate provincial name of " hard-heads." Any one who 

 has traveled much upon them finds his rate of progress most seriously impeded, and re- 

 alizes most fully the fact that they are exceedingly compact. For removing large masses 

 of this variety, the only practicable method is to build large fires upon them. The heat 

 causes flakes of the stone to separate from the mass in angular fragments, and at the same 

 time the mass is rendered brilliantly red from a change in the combination of the iron. 



Every general section crossing the formation encounters this variety. For localities 

 where it is developed better than usual, we refer to East Bennington, Sunderland, East 

 Dorset, Peru, Goshen, Middlebury, Bristol and Starksboro. It is very difficult to 

 decide whether a mass of hyaline quartz in the southeast part of Monkton belongs to the 

 quartz rock or the red sandrock series. Specimens of this variety in the Cabinet are 

 white, red, gray, salmon-colored, and every intermediate shade. 



So much of this rock is granular, that Prof. Emmons has named it Granular quartz. 

 By this term, employed to denote the second variety, we mean a coarser gray or reddish 

 compact granular quartz, or sometimes a sandstone. It is what Potsdam sandstone would 

 become if it were rendered a little more compact. This variety is more distinctly strat- 

 ified than the preceding. We include under it a schistose variety (whose marks of 

 stratification, as recorded, no one will doubt), having often laminae of the eighth of an 

 inch in thickness between the strata. We also include under the term granular quartz, all 

 other varieties of rock, purely quartz, not included in the first and third specifications. 

 These varieties occur upon every section as before, but are best seen in Pownal, Peru, 

 Winhall, Tinmouth, Clarendon, Wallingford, Rutland, and the east part of Bristol. 

 Upon the deposit extending from Rutland to Danby there are several peculiar quartzose 

 varieties associated with it. 



The third variety specified is a fine sandstone or arenaceous quartz rock, closely resem- 

 bling the unaltered Potsdam sandstone. For some cause this variety decomposes very 

 readily, thereby originating the glass sand, so valuable for economical purposes. It is 

 most abundant in Bennington, Shaftsbury, Arlington, Dorset and Monkton. 



The fourth variety was first described in the Geological Report of Massachusetts, and 

 is not always associated there with this formation. It resembled the French buhrstone, 

 which is used for millstones, and was ascertained to be a variety of gneiss, whose feldspar 

 had decomposed and disappeared, leaving the quartz full of cavities. We have noticed 

 that certain rocks, which might be described in the same language, are very abundant 

 among the bowlders of quartz rock at the foot of the Green Mountains. Sometimes the 

 feldspar has not decomposed, in fact in Vermont this is generally the case. So numerous 

 were blocks of this description in Bennington, that formerly all the feldspar used in the 

 Pottery Works was obtained by crushing these bowlders, and separating from the frag- 

 ments the crystals of this mineral. In the conglomerate at East Wallingford feldspar is 

 a large ingredient. It seems often to have been formed by the alteration of the rock ; 

 crystallizing while the mass was plastic. We regret that we have no analysis of the 



