The sixth exhibition of this institute will commence at Louisville, Ky., Sept. 14th, and the directors will be ready to receive goods for exhibition on the 7th. As all machinery, &c, is to be in actual operation, persons intending to exhibit are requested to inform Mr. D. Macpherson, Secretary of the Exhibi-" tion Committee, as to the amount of space and power they will require. THE METALLIC OIL advertised in another column is an excellent article for lubricating machinery. It is durable and economical, and having stood the severest tests for some years past, we can cordially recommend it. We have to thank Commander Thos. Page, of the U. S. steamer Waterwitch, for maps of this survey of the river Parana in that ship.