480 



Scientific Geology. 



ford. It represents a perpendicular ledge about 20 feet square, where 

 mica slate and granite come in contact. The layers of the slate are 

 perpendicular, and this rock is chemically united to the granite. It 

 is easy to conceive how the two rocks should be thus wedged into 

 each other, if we admit that the granite was erupted while in a melted 

 state ; but I am unable to imagine any combination or peculiarity of 

 circumstances, by which such a case can be explained on the theory 

 of the aqueous origin of granite. 



(10) Junction of Granite and M. Slate ; Russell. 



The next case I regard as one of peculiar interest ; chiefly, how- 

 ever, on account of its locality. It is not in Massachusetts : but in 

 Ackworth N. Hampshire, at a remarkable locality of beryls, rose 

 quartz, and crystalized mica. As the traveler approaches this spot, 

 he will observe, while yet several miles distant, a remarkable, conical, 

 half naked peak, chiefly of white granite, shooting up about 300 feet 

 above the surrounding country. This is the hill represented below, 

 as seen on its northwestern side ; along which a road passes. The 

 prevailing rock in the vicinity is gneiss ; but in this elevation it is 

 cheifly hornblende slate, traversed by an enormous granite vein a, and 

 exhibiting at least two protruding masses, b and c, of granite. The vein 

 varies from one half to four rods in thickness, and the mass b, is four 

 or five rods across : c is only 10 feet wide. The general direction of 

 the laminae of the slate is north and south, and the dip from 15 to 20° 

 east : but we have here the most decisive marks of its having been irreg- 

 ularly upheaved and disturbed by the protruding granite. Near the foot 

 of the hill the slate is bent upwards so that the chord of the curve is sev- 

 eral rods long. But it is a curious fact that the axis of the elevating 

 force seems not to have coincided with the direction in which the 

 vein was erupted. For the highest point of the curve of elevation, 



