Twenty thousand years ago, say the geologists, there were great forests where Louisiana now is. Among these mighty trees roamed the glyptodont; the 16-foot armadillo with a tail like the morning-star of the old crusaders, monstrously magnified; the giraffe camel; the titanothere; the Columbian elephant, about the size of a trolley car and with 15-foot tusks; the giant sloth which could look into a second-story window; here the saber-toothed tiger fought with the megatherium; mighty rhinoceroses sloshed their clumsy way, and huge and grotesque birds filled the air with their flappings. As the subsoil packed more solidly, this wilderness in time sunk beneath the waters. The Mississippi built up its sandbars again, storms shaped them above the waves, marsh grass raised the surface with its humus, and another forest grew. This, in turn, sunk. And so the process was repeated, time after time. At different depths below the surface of the ground the remains of these forests are found today, the wood perfectly preserved by the dampness. And through this tangled mass the dredges had to fight their way. It was a task too great for the ordinary type of 20 or 22-inch suction dredge, even with the strength of 1,000 horses behind it. When they met these giant stumps and trunks they just stopped. A. B. Wood, of the sewerage and water department, had already designed and patented a centrifugal pump impeller adapted to the handling of sewerage containing trash. Learning of this, W. J. White, superintendent of dredging on the Canal, asked him to design a special impeller, along similar lines, for the dredge Texas. Results from the invention were remarkable. During the thirty days immediately preceding the installation the dredge had suffered delays from clogged suction which totalled 130-3/4 hours. During the thirty days immediately succeeding installation the total of delays for the same reason was cut down to 71-1/2 hours. The average yardage was, for the earlier period, 152 an hour, of actual excavation; and for the later period, 445 an hour--an increase of almost 200 per cent. The situation had been met. This was the period when the cost of labor and material began to jump. Employers were bidding against each other for men, and the government's work practically fixed the price of supplies.