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 grey limestone, which however was not penetrated to any great depth. In many parts of the excavation, masses of bluish white flint and horn stone were found enclosed in, or encrusting 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 of war and hunting; in one place a magazine of arrow heads was discovered, containing many hundreds of those 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 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.[13] The canal when built was intended for the largest class of boats, but the facilities for navigation have so far improved and the size of vessels increased so far beyond the expectations of the projectors of this enterprise that it is now found much too small to answer the demands of navigation. The consequence is that the canal is looked upon as, equally with the falls, a barrier to navigation. The larger lower-river boats refuse to sign bills of lading, compelling them to deliver their goods above the falls, and as this class of boats is increasing, it promises soon to be as difficult to pass this point as before this immense work was completed. As previous to the undertaking of this canal, so there are now numerous plans proposed for overcoming the impediment; and these do not differ materially from those suggested and noticed in 1804. The only ground upon which all parties agree is, that whatever is done should be effected by the general government, and not left to be completed by individual enterprise.