Niagara Falls 



1809 The rocks which compress the layers of friable shistus at 



Mitchill Niagara are limestone. They are piled up to a great height. 

 They are disposed horizontally, and are of flat or tubular form. 

 Their strength and compactness enables them to overhang the 

 banks, after their foundation of brittle slate has been removed. 

 One of the most prominent and durable of these strata is the 

 table-rock. . . . And it may be regretted, that it will be 

 spoiled whenever the slate beneath shall so far be worn away as 

 to render the incumbent strata of calcareous matter incapable of 

 supporting their own weight. The projecting portions will break 

 off, and descend by their gravity to the subjacent mass of 

 ruins. . . . 



In these calcareous strata, Dr. Mitchill observed the carbonate 

 of lime to predominate. This, however, is not a mere mixture 

 of fixed air with an earthy calx. The rock on being rubbed or 

 broken, emits a fetid or sulphurious odour; evincing that it is a 

 swine-stone or lapis suillus. This disagreeable smell attends the 

 limestone in this and adjacent regions. Dr. M. possesses pieces 

 of it charged with martial pyrites. And the sulphur, clay and 

 iron of this association, are intimately blended with the cal- 

 careous carbonate. The existence of pyritical limestone explains 

 how by the decomposition of the pyrites sulphuric acid is 

 produced, and gypsum formed. 



The calcareous nature of the upper rocks is evinced by the 

 fact, that in the neighborhood of the great cataract as well as 

 at the whirlpool five miles down the river, and at Queenstown 

 two miles further, the inhabitants burn them into limestone for 

 economical purposes. But the material is not always indeter- 

 minate or shapeless. It assumes beautiful crystalline forms. 

 Rhomboidal and cubical crystals are formed on its surface, and 

 in its cavities. The former are of a milk-white colour, with 

 oblique angles. The latter are less frequent, generally found in 

 the same clusters with the others of an almost rectangular figure, 

 and of semi-transparent complexion. Other crystals shoot along 

 the vacuities of the limestone; some of an imperfect hexangular 



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