Wheels, axles, bridges, and rails have all been strengthened to carry their increased loads; but, strange to say, the splices which hold in place the ends of the rails, and which are really short-span bridges, are now the weakest part of a railway. The angle-bar splice has but one-third of the strength of the rail, and its strength cannot be increased, owing to its want of depth. Joints go down under every passing wheel, and the ends of the rails wear out long before the rest. This is not an insignificant detail. It has been estimated by the officers of one of the trunk lines that a splice of proper design and strength would save yearly enough in track labor (most of which is expended in tamping up low joints) to buy all the new rails and fastenings required in some time. It would save much more than that in the wear of rolling-stock. A perfect joint would be an economic device next in value to the Bessemer steel rail. Here is a place for scientific and practical skill. HYDRAULIC ENGINEERING This is one of the oldest branches of engineering, and was developed before the last century. The irrigation works of Asia, Africa, Spain, Italy, the Roman aqueducts, and the canals of Europe, are examples. Hydraulic works cannot be constructed in ignorance of the laws which govern the flow of water. The action of water is relentless, as ruined canals, obstructed rivers, and washed-out dams testify. The principal additions of the nineteenth century to hydraulic engineering are the collection of larger statistics of the flow of water in pipes and channels, of rainfall, run-off, and available supply. It is now known that the germs of disease can be retained by ordinary sand filters, and it is now an established fact that pure drinking water and proper drainage are a sure preventive of typhoid and similar fevers. Very foul water can be made potable. Experiments show that the water of the Schuylkill River at Philadelphia, which contains 400,000 germs in the space of less than a cubic inch, was so much purified by filtering that only sixty remained. This is a discovery of sanitary science, but the application of it is through structural engineering, which designs and executes the filter beds with great economy.