...tre from caves, and the earth under old barns and smoke houses, and from all kinds of nitrogenous waste material. From the saltpetre our chemists could make nitric acid. Our quicksilver came from Mexico , but after the fall of Vicksburg we were cut off from it, and about the same time the supply of sheet copper was exhausted. The chemists found out a mixture of chlorate of potash and sulphuret of a...