Mineralogy and Geology of the White Mountains. 107 



is one and a half inches, and the western, four to six inches wide, 

 and they become, as suggested above, at the distance of some 

 twenty rods north, one larger dike. Fig. 2. 



The occurrence of the two veins in the field, after one had 

 seemed to terminate, and the change of the vein of greater di- 

 mensions from the eastern to the western side, are only some of 

 the phenomena frequently observed in trap dikes, several of 

 which will hereafter be mentioned. 



No. 3. A short distance west of No. 2, crosses the road, direc- 

 tion N. E. and S. W., two feet wide, color very dark, not por- 

 phyritic. 



Trap Dike in Wentworth. 



On the road from Orford to Plymouth, one mile west of Went- 

 worth, above the saw-mill on Baker's creek, is a trap dike in granite, 

 on the left hand close to the road, course north, ten feet wide, 

 color dark gray, and even black, very fine grained and compact 

 in some parts, and fracture smooth ; in others, amygdaloidal, and 

 contains nodules of chalcedony, and numerous very small round 

 white spots of zeolite, which, from its pearly lustre, foliated 

 structure, and low degree of hardness, is, I think, stilhite. Where 

 the surface of the rock is weathered, the stilbite is decomposed, 

 and the cavities are empty. 



Darker specimens strike fire with steel, and all give, when 

 breathed upon, an argillaceous odor, most striking in the softer 

 specimens. 



Half a mile S. E. of Wentworth, by the roadside, are frag- 

 ments of red feldspathic granite, lying on granite m situ, with a 

 very hard, compact trap, adhering to them, but no dike was ob- 

 served. 



Tourmalifies and Diluvial Scratches in Runiney. 



A rounded, well defined ridge of granite, terminates abruptly 

 on the south side of the stage road to Plymouth, and is divided 

 from top to bottom, longitudinally, by fissures, into regular masses, 

 several feet in thickness. On the eastern side is a large vein of 

 granite, filled with large black tourmalines in good crystals. The 

 feldspar of the vein phosphoresces very beautifully with a pale 

 sea-green light. 



Diluvial Scratches, of uncommon distinctness and dimensions, 

 are seen on the west side of this ridge, on an inclined surface, 

 near the road, running east and west. 



