factories in the same system in the new sewerage works of Berlin and Dantzic, increases the running expenses to an extent threatening failure.

The sewage proper of a city is nearly a constant quantity. It is approximately measured by the amount of water daily used in houses and factories. Consequently, the engineer in constructing a system for the removal of sewage proper, can adapt it to a constant flow and make it self-cleansing. On the contrary, rain-fall is an immensely variable quantity. A drainage system for its removal must be of maximum size. When sewage, therefore, is turned into the drainage system, a slow flow will be inevitable much of the time, resulting in putrefaction and the generation of sewage gas, the presence of which within the area of inhabited places dangerously violates the most vital law of sanitation. In the drainage system all conduits are purposely made to let water in. The object is to convey water away from the soil. But a porous drain will strain sewage through into the earth, and gradually pollute it. Consequently, a conduit for the conveyance of sewage must be made tight. Hence the absolute incompatibility of the two ends sought in the same structure. A good sewer is a bad drain. A good drain is a dangerous sewer. Attempts are constantly renewed to attain the double quality of perviousness from without and imperviousness from within, with unceasing and inevitable failure. Sanitarians who are quacks in engineering have tried it in vain; engineers who are quacks in sanitation have tried it equally in vain. Quacks in both engineering and sanitation, sometimes well represented in City Boards of Public Works, obstinately keep up their search for the unattainable, like the seekers for the philosopher's stone and the inventors of perpetual motion.

"Water stored in cisterns is almost invariably poisoned by the way of overflow pipes which discharge into the sewer system of inhabited places and return the dangerous gas. And the drain pipes from cellars and basements generally furnish avenues through which this invisible foe of human life in cities finds easy ingress to habitations. A separate drainage system affords an easy means of guarding against peril from such a source. Sanitary inspectors are often astounded by finding a tube from an ice box, in which choice and delicate food, like meats and milk, is kept, running directly into a sewer pipe. The combined sanitary and engineering quack will tell you, with pitiful ignorance, that the deadly sewer gas is kept out by means of a little-water trap through which a baby could blow with a straw. A separate system, used exclusively for sewage, is the only certain safety against such danger.

“With the clumsy, costly, perilous Combined System in general use for removing water and sewage together, the earth of towns gradually becomes infected with organic matter in a state of putrescence. Hence the water of springs and wells at length becomes polluted and unfit for use. With a separate, properly constructed and properly managed system of impervious pipes for the removal of all sewage, and with other sound sanitary regulations for the

care and removal of solid organic refuse, there is no reason why the spring water and well water in towns should not remain clean and wholesome. Besides, when the earth of inhabited places is kept so clean as to preserve the purity of the water, no exhalations will arise from it deleterious to health and dangerous to life.

"This is not the place to describe in detail the separate sewer systems for the removal of liquid organic wastes from inhabited places. The engineer must conform to the requirements of sanitary science. Any system will be faulty which allows sewage to putrefy at all, either in its source, on its journey from human abodes, or in its outfall. The great principle to be

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kept in view is the removal of sewage (not sewage diluted with vast quantities of surface and subsoil water) without pollution of the soil, without putrefaction, and consequently without generation of sewer gas on the journey. The soil where man dwells is sacred, and it is sanitary sacrilege to pollute it. He who fouls the air that he breathes himself, or the water that he drinks, or the food that he eats, is a barbarian who might learn wisdom from the cat or decency from any swine not demoralized by contact with man. He who fouls the air that another must breathe, or the food that another must eat, or the water that another must drink is a criminal, to be classed with those who maim and kill.

"There are more reasons for such care in the removal of organic wastes from inhabited places than appear on the surface. The chemistry and hygiene of putrefaction are complex, involving many practical considerations. Wherever there is a collection of putrefying organic matter, whether on the ground, in the ground, within a faulty sewer, or under a habitation, there is a tireless foe to health and life. Not only are putrescent collections of garbage, decaying vegetables, manure, offal and human excreta harmful in themselves, by reason of exhalations poisoning the air and leeching liquids polluting the earth; they are also depositories and multipliers of disease germs. Such collections may not produce infectious diseases de novo, but they lessen the vitality of people living in the neighborhood, and thereby lessen the power of resisting epidemics. It is a well known pathological fact that nature struggles to eliminate disease by excretory processes. Accumulations of filth containing excreta may, therefore, harbor seeds of various communicable maladies. Sewer gas, while it may not beget scarlatina, diphtheria, smallpox and other contagious diseases, easily becomes the vehicle of conveying them, through obscure and intricate channels. * * * A foul sewer, swarming with scarlatina germs, may be more dangerous to a neighborhood than an infected school-house.

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"It has been objected in relation to separate systems for drainage and the removal of sewage, that droppings of horses and other animals in the street, steeping in the rain-fall, will be a source of pollution to surface water, rendering it putrescible and, consequently, capable of generating sewer gas. The

simple and effective remedy is cleaning the streets frequently and well. Most cities would thereby be greatly improved, both in appearance and salubrity.

"It has also been objected, that, in quarters where the vitrified sewer pipe system for the removal of sewage does not extend, there the inhabitants must throw the liquid wastes of household life upon the ground. No such necessity exists. Even an isolated habitation in the country should have its sewer pipes, and entirely separate from the drainage system, to convey kitchen slops, wash-water and other dangerous liquids to a place of safety. The reason why typhoid fever, diphtheria, and some other filth diseases are so prevalent in country districts, is that privy vaults so frequently seep into wells, and animal excreta of pig pens and stables are left to poison the earth and the air. The ground about kitchens, super-saturated with slops, very often becomes putrescent in the summer warmth, breeding disease which superstitious ignorance attributes to Heaven. A householder may dispense with his parlor and its adornments, if necessary, but he cannot afford to invite upon himself and family disease and death by neglecting to provide the means of keeping the site of his habitation dry and clean. Laborare est orare-'to labor is to pray'-said the wise old monk, and the most effective prayer for health is to supply every needed hygienic device for the sacred home of the family.

"It is further objected that most of the cities are sewered for the double purpose of removing storm water and sewage through the same conduits, and that we cannot afford to do the costly work over again. It is one of the fates of Progress that faulty methods must be followed by reconstruction. No works last forever, and when we build anew we can do it better. In the meantime the faulty sewers, with their dangerous debouchement into the nearest stream, lakes, or ocean harbor, can be washed out, disinfected, and used exclusively for water-drainage while a supplementary system, with safe out-fall, for the removal of sewage alone, is constructed with proper engineering skill under the direction of sanitary science. The cost of such a supplementary system is not more than one-fourth of that of the prevailing system.”

It will be

Subsoil Drainage.-In some instances it will be necessary to lay special drains for the removal of ground water. found, however, that often the strata are so broken up by digging the trench for the sewer and refilling it that the level of the ground water will be materially lowered. This is especially the case when the soil is made up of alternating strata of pervious and impervious material with an inclination unfavorable to the escape of the ground water.

Nothing connected with designing and building a system of sewers calls for more discretion on the part of the engineer than

proper provision for the ground water. It has frequently happened that long lines of sewer laid beneath the line of saturation have proved to be practically useless from lack of a proper conception of the influence of ground water and lack of proper methods for its removal or exclusion from the sewers proper.

The subject of subsoil drainage will be considered more at length in a subsequent chapter.

CHAPTER III.

THE SEPARATE SYSTEM.

The object of the Separate System of sewers is the complete removal of the sewage proper from towns, in such a manner as shall best subserve the convenience and health of the inhabitants.

To accomplish this object in the most satisfactory manner three things are required, viz.: constant and rapid flow of the sewage, thorough flushing, and adequate ventilation.

Whatever tends to promote either of these three requirements is advantageous to the system and should be adopted. We will, therefore, consider what method of construction and combination of appliances will best attain the end in view. It is evident that to increase the size of the sewers, so as to make them large enough to carry the water of occasional storms, would be detrimental to the efficiency of the sewers, inasmuch as the ordinary flow would be impeded and retarded, and thorough flushing and ventilation made more difficult, if not impossible.

In a majority of cases the storm water can, without causing trouble, run in the surface gutters and ditches until it reaches the natural water courses. Only in large cities, where the water would need to run long distances through the streets, would any underground conduits for storm water be necessary. Where this is the case, either the sewer may be sufficiently enlarged for that purpose, or a separate channel may be provided for the storm water. The necessary length of these storm water sewers will, in any case, be but a small fraction of the whole system.

Roof Water.—On the other hand, if the introduction of a certain amount of roof water into the sewers will insure their thorough flushing whenever there is a sufficient shower, advantage should be taken of such ready means for accomplishing so desirable an end.