474 



Scientific Geology. 



The veins of granite in Massachusetts penetrate only the older 

 rocks; the clay slate being the latest in which they are found. All 

 the older stratified rocks abound in them ; though in quartz rock I 

 have rarely met with any. In gneiss they are very common, espe- 

 cially in the gneiss range east of the Worcester county mica slate: 

 also in the vicinity of New Bedford : and in the southern part of the 

 gneiss range in Hampden and Berkshire counties. Mica slate is 

 penetrated by them and broken up by protruding masses of granite, 

 at almost every step, in the granite range on the west of Northampton, 

 particularly in the towns of Westfield, Blanford, Russell, Chester, 

 Norwich, Williamsburgh, West Hampton, Goshen, Chesterfield, 

 Whately, and Conway. In talcose slate they are very rare: In 

 hornblende slate not common : in micaceous limestone sometimes 

 met with: in serpentine I have never found one. In granite and si- 

 enite they are very abundant : and almost always the ingredients are 

 much coarser than the granite or sienite that contains them. 



For 8 or 10 years past I have been in the habit of taking rough 

 sketches of those spots which I have met with, where granite veins 

 and protruding masses exhibited any peculiarity which I supposed 

 might be interesting to geologists. Of these cases I shall now give 

 an account. I doubt not but a very great number besides these might 

 be discovered by careful research. But to search them out requires 

 a great deal of labor and patience. 



It ought to be premised, that in a large majority of cases,the intrusion 

 of granite veins seems to have produced very little disturbance in the 

 rocks containing them. They would seem to have been open fissures 

 filled by the injection of granitic matter, without materially affecting 

 the walls, except to unite with them chemically. And the same is true 

 to some extent in regard to irregular masses of granite: that is, we do 

 not always see any alteration in the dip and direction of the strata in 

 the immediate vicinity of the granite. Yet in such case we usually 

 find not far distant, an irregularity in the position of the stratified 

 rock. 



In giving the details which follow, it will not be easy to state before- 

 hand any definite order that will be adopted. The most that I shall 

 attempt will be to bring into juxta-positon those cases that are analo- 

 gous. 



The sketch below represents the manner in which the edges of the 

 mica slate lie in contact with a protruding mass of granite in the 



