growth of shells unattached to animal bodies, would have been that of his theory. But he has not established it. He has not even left it on ground so respectable as to have rendered it an object of inquiry to the _literati_ of his own country. Abandoning this fact, therefore, the three hypotheses are equally unsatisfactory; and we must be contented to acknowledge, that this great phenomenon is as yet unsolved. Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong. There is great abundance (more especially when you approach the mountains) of stone, white, blue, brown, &c., fit for the chisel, good mill-stone, such also as stands the fire, and slate stone. We are told of flint, fit for gun-flints, on the Meherrin in Brunswick, on the Mississippi between the mouth of the Ohio and Kaskaskia, and on others of the western waters. Isinglass or mica is in several places; loadstone also; and an Asbestos of a ligneous texture, is sometimes to be met with. Marle abounds generally. A clay, of which, like the Sturbridge in England, bricks are made, which will resist long the violent action of fire, has been found on Tuckahoe creek of James' river, and no doubt will be found in other places. Chalk is said to be in Botetourt and Bedford. In the latter county is some earth believed to be gypseous. Ochres are found in various parts. In the lime-stone country are many caves, the earthy floors of which are impregnated with nitre. On Rich creek, a branch of the Great Kanhaway, about sixty miles below the lead mines, is a very large one, about twenty yards wide, and entering a hill a quarter or half a mile. The vault is of rock, from nine to fifteen or twenty feet above the floor. A Mr. Lynch, who gives me this account, undertook to extract the nitre. Besides a coat of the salt which had formed on the vault and floor, he found the earth highly impregnated to the depth of seven feet in some places, and generally of three, every bushel yielding on an average three pounds of nitre. Mr. Lynch having made about ten hundred pounds of the salt from it, consigned it to some others, who have since made ten thousand pounds. They have done this by pursuing the cave into the hill, never trying a second time the earth they have once exhausted, to see how far or soon it receives another impregnation. At least fifty of these caves are worked on the Greenbriar. There are many of them known on Cumberland river.