were shown before the Suffolk District Medical Society of Massachusetts, the Boston Society of Architects, and others. The results have been published in the "Boston Medical and Surgical Journal," the "American Architect," the "Sanitary Record" of London, and other periodicals.
Without referring now directly to the experiments and investigations, we may consider briefly certain principles which have been established by them. The first and cardinal principle of science as applied to house-drainage is simplicity. In the place of a wilderness of pipes tangled in hopeless confusion about every fixture, modern science demands that there shall be only a simple and positive system which shall act with directness and certainty in every case. The old air-pipes from traps are discarded. There are fewer joints, and the danger from leakage is lessened. Instead of traps that easily lose their seal, notwithstanding the relief-pipes attached, traps are now used that in themselves will resist the hostile influences of evaporation and siphonage. The new system demands that basins, sinks, baths, and water-closets shall be so constructed as to act after the manner of flush-tanks, and scour the whole system of waste-pipes at each discharge. It requires that there shall be no hidden and inaccessible recesses in 
Fig. 6—Showing the Principle of an Anti-siphoning Trap. plumbing fixtures, where filth •may collect and putrefy, so as to become offensive and dangerous. The absolute prevention of serious evils is considered of far greater importance than means to palliate them.
Such, in brief, are the leading principles of the new method which are directly opposed to those of the old. We may look a little more closely into the details of their execution. Simplicity has been secured, as already stated, by the rejection of complicated vent-pipes, and by the adoption of traps secure against siphonage or evaporation. The gradual development of one form of such a trap is an interesting study, but there is space only to outline the principles upon which it is constructed.
The experiments of Mr. Putnam on trap-siphonage showed in what manner the water is withdrawn from traps by siphonic action. It was seen that air, rushing through the seal to fill a vacuum beyond, threw the water upward and outward through
