No. in.] 779 



small quantities at the juncture of the gneiss and primitive lime 

 Stone rocks. A small vein of. Strptntine and caibcnate of lime, 

 occurs in tlie bed of the river. Slight veins of Trcp, are nume- 

 rous, and I may add, to avoid recurrence to the subject, that this 

 rock is prevalent in almost every section of the county, some- 

 times exliibiting extensive Avails, and forming the dyke of most 

 of the Iron ore beds. At. Jay, lower village, it spans the river in 

 a massive dam. The immense and remarkable dyke at Mt. McMar- 

 tin, requires a more particular notice.* It is developed near the 

 center of the mountains, rising abruptly from Avalanche Lake, 

 it traverses the mountain near the summit. The trap is a sienite 

 composed of hornblende, intermingled with grains of felspar and 

 small portions of garnet. It is softer than hyperstene, which 

 constitutes the remainder of the mountain, and has been exten- 

 sively deranged by the action of the elements. A deep gorge 

 has been formed by this disintegration, cutting through the moun^ 

 tain and exposing the whole stratum of the trap. At the en- 

 trance this gorge is 100 feet wide and 150 feet deep, and gradu- 

 ally decreases in both width and depth as it ascends the moun- 

 tain. The trap vein may be traced upon Mt. Mclntyre, in the 

 same course, but less revealed on its bare and precipitous sides. 

 An immense slide nearly parallel with this dyke, has bared the 

 mountain in its terrifiic descent from the summit to the base, 

 leaving a path of naked rock. The debris borne along in its 

 course has nearly filled that part of 'Avalanche Lake beneath its 

 track. This lake, a fountain of the Hudson, is 2.900 feet above 

 its level, and is proba]^ly the most elevated body of water in the 

 State. Its culd waters are only inhabited by- a small lizard. 

 The gneiss rock extends south and west from Lake Sandford over 

 an extensive territory, until it is surmounted by the primitive 

 limestone. In some sections of tlie district gneiss rests upon the 

 hyper^tene. It is inadvertently stated in a State Geological 

 Keport that gneiss does not disclose itself west of North Hudson. 

 It certainly exists in a large expanse in Newcomb.* I trnocd it 

 in Minerva, and funid it extensively disseminated in Jay, iVortli 

 Elba, and St. Armand. The primitive limestone rapidly disinte- • 

 grates* and separates when exposed to the action of the elements. 



• R. CUrk. 



