the orifice of the trap into the waste-pipe, as shown by arrows in the sketch of a pot-trap (Fig. 3). It was observed, too, that a part of the water struck the top of the trap and was reflected back in the form of spray. This suggested the possibility of retaining the water in the trap under siphonic disturbance by repeated deflections from reflecting surfaces. Various experimental patterns of traps were made by Mr. Putnam, as shown in Figs. 4 and 5; and, finally, the form shown in Fig. 6 was found to be anti-siphonic and self-cleansing under all conditions that exist in good plumbing practice. It has four reflecting surfaces to deflect the water from the outlet, and the seal is so deep and the construction such as to enable it to resist both evaporation and capillary attraction.
The general principle that all plumbing fixtures shall act as flush-pots, so that the waste-pipes shall be automatically cleansed, is of great importance. A strong flushing action is secured by making the outlets of the fixtures as large as the waste-pipes
themselves, and by the use of traps having a free water-way, with no balls or mechanical valves to obstruct the flow of waste-water. Aeration is effected by the admission of a free admixture of air into the waste-pipes, automatically forced in by the water escaping from the fixtures above.
The abolition of inaccessible filth-collecting recesses in modern plumbing has necessitated a complete change in the construction of the old forms of appliances with which we have been familiar.
