vide for the removal of slops and sink-water and dispose of urine to a limited extent only. Neither do they provide for the drainage of the soil nor for the removal of surfaceConvenience also is not fully served by their use.

water.

ART. 4. PNEUMATIC SYSTEMS.

In the Pneumatic systems the fæces only are removed, the house drainage, surface- and subsoil-water requiring a separate system of sewers or utilizing the gutters. The most widely known of these are the Liernur and the Berlier-the first used principally in Holland, the second in Paris. These two are practicable under certain conditions only and will not be described at length. Their object is to remove the sewage at frequent intervals through pipes, by means of compressed air or a vacuum, to a central station, there to be disposed of in some way, usually by being manufactured into a fertilizer. The great cost of these is prohibitive to their introduction into small cities and towns, and on account of their limited applicability, as well as for practical and sanitary reasons, their adoption in future designs is improbable.

The Shone system, which is used to some extent in England and her colonies and in this country, although classed among the Pneumatic systems, is really not in itself a system, but an application to the water-carriage system of a method of pumping sewage by the direct action of compressed air. It will therefore be considered under the head of the Water-carriage System.

ART. 5. WATER-CARRIAGE SYSTEM.

The Water-carriage system has now been so almost universally adopted where any improvement upon the primitive privy has been attempted that the term "Sewerage System"

is ordinarily used without further qualification to refer to it. When properly constructed and managed it is certainly deserving of its popularity, being the best and cheapest method yet contrived for the removal of sewage.

As its name implies, its distinctive characteristic is the removal through conduits, by gravitation, of sewage which has been greatly diluted with water. It meets the first principal requirement of a sanitary system (Art. 1)—it removes all house-wastes and removes them immediately. It also serves the secondary but by no means unimportant purpose of removing the surface-water and draining the ground. Its convenience also is excelled by no other system. Moreover, where the territory is quite thickly populated—as in the average town-it is in the end cheaper than any other system. The two most weighty arguments against it are the large amount of water needed for its efficient working, and the pollution of streams and waste of the valuable manurial properties in the sewage when this is emptied into river or sea, as is frequently done. Victor Hugo in his "Les Misérables" devotes a long chapter to the "Crime of the Century" involved in this waste. But whether this matter is ultimately wasted or its use by man only deterred it is not necessary to discuss.* The all-convincing argument with any but the sentimentalist is that, while there may be manurial value in sewage, no commercially profitable method of utilizing it has yet been found. The best disposition to be made of it is therefore that which is least harmful, unpleasant, and expensive, and in most cases water carriage enables us to provide such disposition.

The argument that its proper working involves the use of large quantities of water is undoubtedly true. But where water-works already exist this objection has little force-less in this country than abroad, where 20 to 40 gallons per capita is considered a liberal allowance for water-consumption: * See page 24, last paragraph.

while in this country our small cities must provide two or three and the large ones five or six times this amount, which, with in many cases a small percentage additional for flushing, is usually sufficient and no difficulty is found in providing it. Some expense, however, is frequently incurred for flushingwater and to this extent is there force to the objection.

Places which are without a general water-supply or the general use of individual power-supplies are barred from the adoption of the Water-carriage system. For such the best plan is to adopt the Earth-closet system until such time as water has been introduced into most of the dwellings, when a Water-carriage system may be initiated, the Earth-closet pails being continually relegated, as the conduit system is extended, to the outskirts of the town, where the growth will probably keep a year or two ahead of the water-supply and sewer-construction.

Other objections are sometimes raised to the Watercarriage system which are either equally applicable to all systems or which are the result of prejudice. The possibility of the introduction into dwellings, through the house-connections, of sewer-air (which is not a gas") is one of these, and is certainly a real one. But the resulting danger is not so great as that connected with similar evils of other systems, and it is preventable by careful designing and construction of the sewers and house-plumbing.

ART. 6. COMBINED AND SEPARATE SYSTEMS.

It is generally conceded by sanitarians that where the conditions render it possible the Water-carriage system should be adopted. This system, however, has been subdivided. into the Combined and the Separate systems. The terms "Combined" and "Separate Separate" refer to the two classes of waters which it is desirable to remove-rain-water and house

sewage. In the former system these are carried in a common conduit; in the latter the house-sewage is removed through small sewers, the storm-waters through other large ones or in the gutters, or partly in one and partly in the other.

The comparative merits of these is a theme much discussed and upon which unanimity of opinion has not yet been entirely reached. It will most probably be reached by mutual concession, for there are undoubtedly substantial arguments in favor of each. In some cases the one, in some the other, is most applicable. In many, if not a majority of, instances a judicious combination of the two will work to better advantage than either alone.

There is neither space nor necessity to quote in this work all the arguments advanced for and against each of the systems, or even to attempt to specify them all in detail, since the systems will be treated as coöperative rather than as rivals; for such is the relative position now assigned them by the best authorities. Their respective advantages under varying conditions will be treated of in Chapters III and VII. It may be well, however, to give in this connection a short statement of the points at issue between the two systems.

Either system must, if providing for storm-water, include sewers of large size-2, 3, even 15 or 20 feet in diameter. Yet during nine tenths of the time the amount of sewage flowing is no more than could be carried by pipes of from 4 inches to 2 feet in diameter.