GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. l8l 



precipices, well situated for quarrying. In Kcclron there is an interest- 

 ing narrow dyke, from six to ten inches wide, of a light-colored soft 

 material, readily fashioned with a knife. Along the railroad one sees 

 other very pretty dykes of trap crossing the valley, and probably connect- 

 ing with similar exposures upon Mt. Webster. The Conway granite may 

 be traced to Cow brook, along the railway. It is followed by the Albany 

 variety, containing several trap dykes of great interest. In the numerous 

 cuttings below it is interesting to observe the change of color from 

 greenish or grayish to red, in proximity to each trap dyke, occasioned by 

 the oxidation of the iron present. 



Frankenstein cliff is the name of the north-eastern extremity of the 

 Mts. Lowell-Andcrson-Nancy range, where it is cut by the railroad. It 

 is known further by the very high iron trestle-work adjacent on the south. 

 This cliff is chiefly sienite for about half a mile along the railroad, north 

 of the iron trestle. It resembles the rock of Mt. Whiteface, north part of 

 Passaconnaway, and much of what is called the "Chocorua granite." At 

 the north end of the ledge the hornblende is replaced by mica for a few 

 rods. Small cavities, lined with quartz crystals and containing a little 

 chlorite, are common in this ledge. 



This sienite seems to occupy the position of the Chocorua rock, as 

 indicated heretofore, for in coming south from the Willey house we found 

 the usual succession of granites, — the Conway first, then the Albany, and 

 lastly the sienite. Near their several junctions there is an intermingling 

 of the adjacent varieties. Likewise in going south we find the reverse 

 order of succession beyond the iron trestle, though there are other varie- 

 ties which make the order of distribution somewhat perplexing. The 

 overlying place of the sienite is very clear. Where a reddish hard rock 

 appears, south of the trestle, one can see the sienite ledge above descend- 

 ing to the cliff from the south-west ; and immense blocks of the upper 

 rock have been detached by frost and fallen down to the level of the 

 railroad. The appearance of the sienite belt rising to the south reminds 

 us of the similar position of the Breccia granite on the south-east face of 

 Mt. Willard (page i68). At the lowest accessible point in the valley, at 

 the crossing of the Saco river by the carriage-road, not very far below 

 Frankenstein, there is an unmistakable extensive development of red 

 Conway granite. The upper and lower members of our granite series 



