186 QUARTERLY JOURNAL. 



The Sparry limestone forms a long belt, running near the base of 

 Petersburgh mountain, north through Arlington in Vermont. A point 

 where it may always be recognized, is the tunnel for the Great 

 Western Railway. The tunnel is 500 feet in length, and 200 feet 

 below the surface, and is wholly in this limestone. The adjacent 

 slate is black, in consequence of decomposed pyrites. This lime- 

 stone contains some alumina and magnesia. It may be distinguish- 

 ed by its checkered appearance, which is owing to narrow seams of 

 white calcareous spar traversing a dark blue ground ; for there are) 

 certain other limestones which resemble this, and from which it cannoK 

 be known with certainty unless inspected in place. This rock de^ 

 composes slowly, and thus makes but little soil. Slate of a coarsei 

 kind succeeds the sparry limestone eastwardly ; and it is immedi 

 ately to the east of the sparry limestone, that the range known aa 

 the Taconic mountains occurs. These are almost entirely made up 

 of a silvery gray slale, in which we find rarely thin beds of impure 

 limestone : it is called magnesian limestone. This rock forms : 

 warm soil ; but most of the country where it is found, is high land 

 It abounds in masses of milky quartz, in the cavities of Avhich wi 

 find carbonate of iron. Chlorite also is common, and is mosth' 

 associated with the quartz. 



At the eastern base of the Taconic range, we find the Stockbridg ' 

 limestone. It is white, gray or clouded, and is frequently a dolomitij 

 or a magnesian limestone. When thus composed, it is often ver j 

 friable and tender, and subject to disintegration. It is also frequentl; j -*' 

 siliceous, and then it is equally disposed to crumble. It forms, in bot J * 

 cases, a warm and excellent soil for maize and grass. 



Another range of slate succeeds the Stockbridge limestone o| 

 the east ; but as its characters are nearly the same as that whic 

 forms the Taconic mountains, we pass it by without further remark 



The last rock of this system, is the Granular quartz. The lowes 

 part of it is a puddingstone or conglomerate, sometimes a ferrugi 

 nous breccia. The main body of the rock is an indestructible fine 

 grained sandstone. Sometimes, however, it is granular and friable 

 and then forms the white sandy quartz. The soil it makes is coarse 

 and siliceous in an eminent degree. 



The rocks which we have now imperfectly described, form belt|jj 

 which run nearly north and south to an indefinite extent, and pa 

 rallel with each other. Sometimes they are intercepted by the opera 



