The first stratum of rock was a light, friable slate, in close contact with the limestone, and difficult to disengage from it; this slate did not, however, extend over the whole surface of the rock, and was of various thicknesses, from three inches to four feet. The stratum next to the slate was a close, compact limestone, in which petrified seashells and an infinite variety of coralline formations were imbedded, and frequent cavities of crystalline incrustations were seen, many of which still contained petroleum of a highly fetid smell, which gives the name to this description of limestone. This description of rock is on an average of five feet, covering a substratum of a species of cias limestone of a bluish colour, imbedding nodules of hornstone and organic remains. The fracture of this stone has in all instances been found to be irregularly conchoidal, and on exposure to the atmosphere and subjection to fire, it crumbles to pieces. When burnt and ground, and mixed with a due proportion of silicious sand, it has been found to make a most superior kind of hydraulic cement or water-lime. The discovery of this valuable limestone has enabled the canal company to construct their masonry more solidly than any other known in the United States. A manufactory of this hydraulic cement or water-lime is now established on the bank of the canal, on a scale capable of supplying the United States with this much-valued material for all works in contact with water or exposed to moisture; the nature of this cement being to harden in the water; the grout used on the locks of the canal is already _harder_ than the _stone_ used in their construction. After passing through the stratum which was commonly called the water-lime, about ten feet in thickness, the workmen came to a more compact mass of primitive gray limestone, which, however, was not penetrated to any great depth. In many parts of the excavation masses of a bluish white flint and hornstone were found enclosed in or incrusting the fetid limestone. And from the large quantities of arrow-heads and other rude formations of this flint stone, it is evident that it was made much use of by the Indians in forming their weapons for war and hunting; in one place a magazine of arrow-heads was discovered, containing many hundreds of these rude implements, carefully packed together and buried below the surface of the ground. The existence of iron ore in considerable quantities was exhibited in the progress of the excavation of the canal, by numerous highly-charged chalybeate springs that gushed out, and continued to flow during the time that the rock was exposed, chiefly in the upper strata of limestone.--_Louisville Directory for 1835._--FLAGG.