HISTORY OF DERRYFIELD. 29 



ing the dissolution of the ice-cap these masses were released and 

 fell headlong, sometimes for great distances, striking the earth 

 with a force sufficient in many instances to shatter them in 

 pieces. This theory would not only answer the question raised 

 but would also account for the varying intervals between the 

 parts of the pareiit mass. In our field studies we have frequent- 

 ly met with such a rifted fragment and queried as to the where- 

 about of its companions. We need hardly add that the eviden- 

 ces of rock-weathering and the accumulation of moss or lichen, 

 even upon the riven surfaces of the bowlders alluded to, show 

 the fractures to be of great age, and that they must necessarily 

 be referred to the time of impact at the point of deposition. It 

 is quite easy to make allowance for the character of the surface 

 upon which the rock chanced to strike ; the problem of the dis- 

 tance through which it fell we gladly leave to the physicist. 



Garnet-bearing gneiss is quite common hereabout, some of 

 the ledges near Rock Rimmon containing good specimens, but 

 probably of no commercial importance. No valuable minerals 

 have ever been found here, so far as we are aware, although 

 beautiful crystals of quartz, felspar, hornblende and tourmaline 

 are encountered, and small quantities of graphite are found in 

 local ledges. Small but finely-polished porphyritic pebbles are 

 found near by in the bed of the Merrimack, brought down from 

 the neighborhood of Moosilauke mountain by way of Baker river 

 and the Pemigewasset, others reaching us by way of the Winne- 

 pesauke. Larger fragments of porphyritic rock are found at 

 various levels, even upon the water-shed ridges, which points to 

 the wide dispersion of this peculiar rock, as we understand it is 

 not found in place nearer than the region of Winnepesauke lake. 

 The text-books will sufificiently describe the character and trace 

 to their habitat other transported minerals, some of which came 

 to us from the Laurentian hills or even the remote wilds of 

 Labrador. 



