to settling of the walls, floors, and fixtures. Sometimes, also, large holes are made in the traps or leaden pipes by rats. I have in my possession examples of all these varieties of defective traps, taken from some of the best houses in this city, and the existence of which defects was not suspected until disclosed by the plumber. The traps, to be effective, it is unnecessary to say, must be kept in perfect working order, for this is a dangerous door to be left ajar, even for one moment.
The complete protection of our houses against sewer-gas will not, however, be accomplished when a trap shall be invented which shall be liable to no accidents and shall never fail. The trap is a matter of small consideration compared with the whole amount of plumbing work, of which it constitutes only a fraction.
The Pipes.—Professor Doremus demonstrated at the Academy that gases would pass readily through brick and stone, and through unglazed earthenware, even, in one instance, against a resisting pressure of two and a half feet of water, and in another against the pressure of a column of mercury thirty inches in height. The experience of every practical plumber confirms these experiments. Gases escape more or less readily, also, through iron pipes.
Lead and iron pipes are subject to the erosive action of the gases, and of various reagents. They are also, like the traps, liable to be broken by the settling of walls, floors, and fixtures, and they are occasionally broken by their own weight. The leaden pipes may be eaten by rats; at the jointings, they are believed occasionally to be perforated by galvanic action. In nearly all these cases the holes are at first small, but frequently a large number of these small holes will be found at the same time in different portions of the plumbing. These are the minute perforations to which Dr. Billings probably referred when he said, "there is more danger from a pin-hole in a pipe than from the traps"; for, while it is true that a large proportion of the germs perish for want of a favorable soil, it is equally true that one germ of a malignant type, conveyed into a system fully prepared for its nutrition, is as fatal as a thousand. Colin estimates that one bacterial rod, under favorable circumstances, will produce 281,500,000,000 in forty-eight hours; and that, were it not for the unfavorable circumstances incident to its situation, it would fill the ocean in five days. It is not impossible that this one "pin-hole" might admit the typical bacterium into a typical soil.
Mr. Charles F. Wingate, sanitary engineer, says:
