52 HENTZ OX A NEW SPECIES 



and containing imbedded prismatic chrystals of 

 brown mica. Slate of various kinds, occasionally 

 alternating with a peculiar novaculite bordering on 

 hornstone, and dipping at an angle of not less than 

 45 constitutes the principal part of this formation, 

 and. is overtopped as in the Alleghanys, by elevated 

 ridges of sand -stone.* 



* In this chain of mountains, which continues north-easf- 

 ward towards the sources of the St. Francis, two miles north 

 of the village of St". Michael, at the lead-mine of La Motte, 

 Mr. Schoolcraft observed, what he calls a vein of granitic rock, 

 of a red color, and containing very little, mica, he asserts it to 

 be four or five miles wide, and traced its continuance for 

 twenty or thirty miles; as he adds, at the same time, that it is 

 used for mill-stones, I can scarcely doubt for a moment, its 

 identity with the transition conglomerate which Mr. Bradbury 

 and myself examined, in 1810, employed for the same purpose, 

 a few miles from St. Louis. What the green-stone porphyry 

 may really be, I cannot pretend to say, though it may very pos- 

 sibly exist in that quarter. Mr. Bradbury visited the spot and 

 obtained specimens of the micaceous iron-ore, which is said to 

 form a mountain mass near to Bellevue (Washington county.) 

 These united facts, tend to prove the continuation of the tran- 

 sition chain of mountains beyond the valley of the Mississippi, 

 but they ought not to be confounded with the chrvstalline gra- 

 nitic formation of the sea-coast and the northern Andes. 



