The model of the Gatun locks showed the boy everything, just as it will be when the canal is opened for traffic in 1913. There was the wide Gatun lake, surrounded by the tropical forests, the great Gatun dam, and the series of locks in one solid mass of concrete. These locks when completed will be 3,800 feet long, and their tremendous height and thickness can be seen from the pictures of the work as it is actually being carried on. In the model there were perfect little ships on the lake and going through the locks. Besides the many present day uses of cement some of the concrete enthusiasts are suggesting that heavily reinforced concrete be used in place of steel in making bank vaults, as they declare that the material will resist the keen tools and the powerful explosives of bank robbers even more successfully than the hardest steel. Then too, at the cement show, the boy saw, besides models of big works and examples of all kinds of concrete construction, exhibits of the various methods of placing steel bars and steel network in the cement to make it stronger, and the different machines used in mixing concrete and in making Portland cement, which is the binding element in concrete. As concrete is a material that can be mixed by an amateur and used for a great many purposes, the booths where mixing and simple uses were demonstrated attracted a great deal of attention. For instance, in the last few years the farmers have found out that they can make watering troughs, drains, floors for stables, hen houses, and even fence posts, of concrete just as easily as they can of wood or iron. Moreover, the articles thus made will last practically forever. All that is needed is a supply of Portland cement, and a little careful study as to the best way of mixing it with the proper amounts of sand and gravel. The amateur has best results if he starts modestly and takes up the use of reinforced concrete after learning how to use the material in its simple form. One of the most interesting uses of reinforced concrete for the amateur who has learned something of the craft is in making a good, seaworthy rowboat, or even a small motor boat. Poured boats are strong, graceful, and durable. If they are properly made there never is any danger of their leaking, and by a little extra pains it is possible to make them with air-tight compartments so that they are non-sinkable.