Indeed, that water, especially when not in motion, will absorb gases, including putrefactive and septic germs, is a well-established fact; and it is equally well established that germs will live and multiply in water, and that they will even, in some cases, survive the action of frost upon the water. Germs in a condition of extreme desiccation and apparently long dead will, on being treated with moisture, if other circumstances are favorable, become revivified and developed into their most perfect and active forms.
It being indisputable that germs may be absorbed by water, and that they may multiply in water, it seems irrational that they should not by evaporation, or by the means of minute bubbles generated by decomposition of organic matter in the water, or by agitation of the water, escape into the surrounding atmosphere.
Professor Kerr, in an address before the British Civil and Mechanical Engineers' Society, said:
Must we, then, accept as final the experiments made by Dr. Carmichael, and perhaps a few other experimenters? May we safely conclude that the gases and germs contained in the sewers can be effectually excluded by water-traps? That well-sealed water-traps afford some protection can not be questioned; but the experiments of Carmichael seem to me far from having rendered it certain, or even probable, that they insure absolute safety.
The reader will observe, however, that, even if we admit that the experiments of Carmichael establish all that has been claimed for them, it is still none the less a fact that the water-traps give us no protection when they are empty or defective; and examples abound in the experience of almost every plumber, in which the traps are found empty, either in consequence of the direct pressure of the air from below, or of siphonage, or of leakage; the leakage being sometimes due to the erosive action of the gases, to which action the traps are especially exposed, and sometimes to cracks occasioned by contraction and expansion, resulting from the alternate admission of hot and cold water,