264 SURFACE GEOLOGY. 



BOULDERLESS ArEAS. 



In New Hampshire no considerable regions are devoid of boulders, 

 except areas of sand where the stones are concealed by deposits of later 

 age. The nearest approach to a boulderless area is in the limestone 

 regions of Cornish and Colebrook. In eastern Vermont the absence of 

 boulders over the same formation is very conspicuous, as may be seen 

 in passing up Wait's river and the east branch of White river. The 

 boulders of the underlying rock decompose readily, and it is believed 

 that though once as common as the average of granite blocks in New 

 Hampshire, they have been disintegrated by atmospheric agencies, leav- 

 ing very few signs of glacial work. Occasionally lines of granite boul- 

 ders occur in this calciferous area, enough to show that the glacier did 

 not slight it. Such boulders would furnish excellent studies of the radial 

 dispersion of fragments, as their distribution could be easily made out. 



On the contrary, some kinds of rock seem almost incapable of decom- 

 position, and leave the fields profusely strewn with them, The porphy- 

 ritic gneiss and the Exeter sienite areas are remarkable for the great 

 amount of rough blocks of their own kind scattered over them. They 

 are mostly those that have just started on their travels. Between Dover 

 and Exeter the loose fragments of sienite scattered over the area occu- 

 pied by this rock are numberless, and commence abruptly on the north- 

 west side. One knows that he has reached the sienite rock by the 

 numerous blocks of it seen long before a ledge can be found, it may be. 

 I suppose their abundance is to be explained by their difficult decompo- 

 sition. 



Large Boulders. 



Although our state is noted for the great abundance of boulders 

 strewn over its surface, it is only quite recently that I have seen boul- 

 ders in our limits larger than any of which mention has been made in 

 the writings of American geologists. They were brought to our notice 

 by His Excellency Governor Prescott. Regret had been expressed to 

 him that no boulder had been found in the state equal in size to those 

 known to exist in the neighboring states. As if he felt the credit of the 

 state impaired by the imputation, he immediately searched the neighbor- 



