At the time when these lectures were first delivered, in the winter of 1899-1900, the plumbing laws of Bos-ton and of nearly every other city of the United States enforced a system of piping and trapping which almost doubled the cost of the work in new buildings and more than doubled it in repair work over what was necessary, besides greatly lessening its convenience and safety.

Every fixture was required to have a separate trap, and every trap had to be independently revented by a special "back vent" pipe extending up to the highest fixture in the building. A disconnecting trap was required between every building and the public sewer, which prevented the best and only known really effective method of ventilating the sewers; and no better method of jointing cast iron pipes was allowed than the unscientific, unreliable and very costly lead calked bell and spigot joint.

These worse than useless and very burdensome requirements have held the people like a vise for the last quarter of a century in spite of the protests during all that time of many of the leading sanitary engineers and plumbers.

Fig. 2. Complexity and Danger. Type of system of extreme complication to which we are tending.

Fig. 2. Complexity and Danger. Type of system of extreme complication to which we are tending.

Fig. 3. Simplicity and Safety. Type of system recommended as a substitute.

Fig. 3. Simplicity and Safety. Type of system recommended as a substitute.

Within a very few years, however, some of the more wide awake and progressive cities have seen the folly of this course and have given their citizens the benefits which the modern simpler and more scientific methods and discoveries have provided, and every year is adding to their number. But as the plumbing laws of the majority of places are based upon the ideas of more than a decade back, the only possible way to present anything of the least value in this important department of architecture is to break entirely away from the conventions of ordinary practice and base all our conclusions upon direct personal investigations and absolute demonstration. Our treatment must therefore necessarily become largely critical and argumentative throughout, and, although this method of handling the subject is certain to arouse from marry quarters adverse criticism and possibly some bitterness, it is nevertheless evidently unavoidable, and will also have the great advantage of making the matter vastly more interesting and we hope much more intelligible to the reader.

The arguments used by the writer as early as 1884 in behalf of this simpler plumbing system have been of late greatly reinforced by the discoveries of the bacteriologists. The data they have furnished and their significance from a sanitary standpoint have been summarized by him in his publications before 1909, as follows:

(1) A sound water seal affords a reliable barrier against the entrance of sewer air and all kinds of germs.

(2) Dust and germs falling into water or against the wet surfaces of sewers and drain pipes are, under normal conditions in the drains, arrested and prevented from rising again into the air so long as the surfaces remain wet.

(3) Abnormal conditions prevail in the drains when splashing or bubbling occurs in the sewage under the influence of which fine droplets may be projected into the surrounding air. If these droplets contain germs and are minute enough to be wafted in the air currents passing through the pipes the germs therein may remain in the air until they again fall against the wet surfaces. Even germs have a definite weight and the speed of their descent under the influence of gravity has been calculated, which gives also the speed of an air current necessary to support or move them.

(4) It is possible that small particles of sewage which have dried against the upper parts of the walls of the sewers may be detached therefrom by air currents and in this manner under rare instances allow of the escape of germs into the sewer air. The probability of this action is denied by some investigators, but affirmed by others. It may be admitted as a possibility.

(5) Disease germs seem to be unable to survive long in sewage, the non-pathogenic germs therein far outnumbering them and destroying them by their products.

(6) Fewer germs are found in the air of sewers than in the outer air above the sewers, and those which are found in the sewer air are dissimilar in kind from those in the sewage but similar to those in the outer air.

(7) The number of germs present in the air of well ventilated sewers exceeds that in less well ventilated sewers, and varies with variations in the content of the street air, implying that their origin is from without and not from within the sewer.

(8) The majority of investigators have failed to isolate specific disease germs from the air of sewers, and it may be stated in general terms that they are not to be found there under normal conditions. Yet a few well known investigators have obtained cultures in the air of sewers of germs apparently coming from the sewage under normal conditions, and it is generally admitted that the splashing, bubbling or drying of the sewage may release them under rare conditions in good practice. Their numbers in sewer air must, however, in properly constructed sewers be so small in the whole volume of the sewer air, that their effect regarded from a sanitary standpoint may be considered as negligible.

From the above data and from his own experiments the writer has derived the following general conclusions affecting Sanitary Engineering.

(I) It is known that disease germs, especially those of consumption, may be disseminated in the air above the sewers, and may, especially in times of epidemic, abound there in large numbers, and unquestionably in larger numbers than in the air of the sewers themselves.