favor such a system, that it has at last had marked effect in this country, where, indeed, it has received important modification and amendment. Many smaller towns, for which sewerage was recently not thought necessary, are now discussing the propriety of introducing complete works, or are actually carrying them out, advantage being taken in many cases of the greater economy and cleanliness of the separate system. Indeed, this system is being considered for portions of our larger towns in some cases, in others for whole towns. Baltimore, for example, where the existing sewerage works are confined to some dozen miles of storm-water conduits laid in the low-lying parts of the town where surface water used to accumulate, is now actively considering a project submitted by its engineer, Mr. Charles H. Latrobe, for the complete sewerage of the whole city,- over one hundred miles,-on the system of the entire separation of storm-water, as carried out in Memphis. New Orleans has adopted the same system, to be executed when, if ever, it shall be able to procure funds for the purpose.

Ordinary brick sewers, as built from immemorial time, are practically very far from being impervious to water. The original purpose of their construction has usually been to carry away storm-water flowing on the surface of streets and of private property; but one of their most beneficial offices has been found to be the incidental removal of the surplus moisture of the soil,- an effect the influence of which upon public health has always been great. So obvious, indeed, has been the advantage of such soil drainage that, where tightly jointed vitrified pipes are used in heavy soils it is usual, in the best practice, to lay porous draining-tiles in the ditch, or, in practice not so good, as in recent work at Newport, to leave the lower part of the joints of the pipes uncemented, securing in this way, when the ground is saturated, an efficient subsoil drainage. Unfortunately, this method secures also the unintended result of allowing foul sewage to spread itself throughout the soil during dry seasons, poisoning the ground and robbing the heavier part of the sewage of its requisite means of transportation, stranding it as a deposit in the pipes.

The influence of subsoil drainage on the general health of the people, and especially in removing or mitigating fever and ague in malarious regions, has been quite as marked in the case of drainage works carried out in country districts for purely

agricultural reasons. The result of such drainage in England, in districts which were formerly extremely malarious, has been most important and lasting, and it is now the accepted belief on all sides that the sovereign remedy for fever and ague is the complete drainage of all moist land in the neighborhood.

The history of house drainage during the past fifty years is the history of a most rapid and satisfactory progress, from the mere introduction of convenient channels for the removal of what would otherwise have to be carried out of the house by hand, to a process whose intimate relation to the health of the people is universally recognized. It has more recently exhibited a steady growth from the "modern conveniences" scattered throughout the house by the profuse hand of the plumber, with no regard to the effect on the atmosphere of the dwelling, to the "sanitary drainage" which is now so jealously guarded by intelligent Boards of Health, and in which convenience is made secondary to conditions of cleanliness and purity. It is safe to say that we have now the prospect of securing, at an early day, a constant regard for healthful conditions in the introduction into the houses of rich and poor of those appliances for convenient and more civilized living which the whole people is so fast coming to demand.

A review of this progress discloses a remarkable change in public sentiment. Twenty years ago the number of persons who paid the least attention to the sanitary accompaniments of modern living was altogether insignificant. Later, the influence of the pens and tongues of a few enthusiasts, and of far fewer philosophers, began to be felt, and that element of society which formerly expended its enthusiasm on phrenology and kindred "sciences" began to take up sanitary science as a more promising field for the exercise of its energies. This led to the condition which now prevails, when drainage is elevated to a position of undue prominence; when, with few exceptions, all the ills that flesh is heir to are ascribed to wet ground, foul soil, defective drains, and that great bugaboo of them all, "sewer-gas"; when defective ventilation, stove heat, furnace heat, bad food, and worse drink are allowed their littledisturbed sway, the majority of their victims being charged to the account of bad drainage. The capital of the nation is notoriously the place where "malaria " plays its wildest pranks and finds its most distinguished subjects. Its site has defects,

and its saturated soil is undoubtedly most objectionable. But in all the outcry against the malaria of Washington we hear little of the whisky, and the late hours, and the dissolute life to which, probably, a more just estimate would ascribe the greatest proportion of its morbidity and of its mortality.

These remarks are by no means intended to belittle the office of proper systems of drainage in improving the public health, but rather as a precaution against that general disappointment which must follow the demonstration of the patent fact that perfect drainage is not the only requirement of perfect living. With this limitation, too much importance can hardly be attached to the subject; nor can too much earnestness be employed in urging forward every movement which looks to the removal of filth and of undue soil-moisture.

It cannot be pretended that the conditions of sanitary perfection are known; but we may safely claim that the intelligent investigations of the past few years have led to a very important increase of our positive information on the subject. There is no doubt that some of the well-accepted theories of the present day are destined to be set aside by future investigation; but, on the whole, they constitute a very good and reliable foundation for systematic work. They contain a sufficient element of certainty to justify local Boards of Health in establishing rules and regulations, the enforcement of which, whatever their imperfections,— and it is to be remembered that such rules have to be prepared for universal application, not alone for those who desire and are willing to pay for the best work,—cannot fail to bring about a marked improvement in the condition of life of all classes of the people.

The assumed basis for the best present practice,-most of which will probably stand the test of time,—may be fairly stated as follows:

All ordinary domestic waste matters, whether offensive or inoffensive, when first produced, become to about the same degree offensive when putrefied. They also become to about the same degree dangerous, save that some may carry specific germs of disease, which are absent from others. All such matters should, therefore, be removed entirely beyond the house and beyond the limits of population before their putrefaction sets in The objections attaching to the decomposition of these substances attach in like manner, but in less degree, to such of

their elements as adhere to the walls of the channels through which they are removed; i. e., it is important not only to consider the removal of the great bulk of our filth, but also to guard against evils arising from the decomposition of the adhering particles which mark the course it has followed.

The removal of waste matters by transportation in water has such preponderating advantages over all other systems of treatment, including the earth closet,— that it is not worth while, for general practice, seriously to consider any other than the water-carriage system. The removal of solid matters in a stream of water requires a sufficient depth in the flow to carry the solids along, and a sufficient velocity to prevent sedimentation. As these elements-depth and velocity-must always work together, the size of the channel through which the stream runs is most important. An amount of water that would fill a large pipe half an inch deep, would fill a sufficiently smaller pipe an inch deep. Ordinary focal solids are readily transported in water an inch deep, while in water of only half that depth their buoyancy would be too much reduced, and the amount of their surface receiving the impulse of the flow would be too small for their prompt transportation; so that, unless the velocity were so great as to break down the mass, they would remain in the chan. nel. Some of the substances reaching our drains are of too firm a consistence to be broken down by the velocity of ordinary streams, and these often form the nucleus about which fouler things gather to create accumulations. Therefore, it is important, with regard to all drains which do not run full, that their diameter be so restricted as to give the required depth to their flow. There is another consideration of equal importance which must always be kept in view: the velocity of the stream remaining the same, the depth of the flow will be in proportion to the diameter of the pipe and to the quantity flowing through it. Therefore, as the quantity supplied in ordinary house drainage is fixed, the diameter of the pipe must be so restricted that, at the velocity with which it flows,-varying according to the rate of inclination, the given fixed volume will secure the required depth. It is not, of course, possible to maintain at all times a cleansing depth of flow in any house drain; but it is possible, by regulating the diameter of the conduit in accordance with the volume flowing at the time of greatest use, and with the rate of inclination, to make sure that at some time during the day, and

generally several times during the day, there shall be a sufficient depth of current to wash away what the straggling flow may have left behind.

In those parts of the house drainage where the conduit is filled with water, it is necessary to give, at least at frequent intervals, a sufficiently rapid movement to the whole mass to carry away whatever may have been deposited in these filled portions by slighter discharges. Practically, this observation applies mainly to the case of traps, where a bend is introduced in the course of the pipe to hold water, as a "seal" to separate the air of the outer drain from the air of such pipes as are open to the interior of the house. In this case, velocity has to be given not only to water occupying a portion of the pipe, but to its full contents, so that the diameters of traps should be, other things being equal, considerably less than the diameters of the pipes leading to them and from them.

One of the most serious difficulties met with in practical work is what is known as "siphonage," that is, the sucking out of the water of traps by the rarefaction of the air in the outer pipe, caused by the passage of liquids or air through it or across its mouth. The tendency to siphonage is greater in small traps than in large ones, the same suction being brought to bear on a smaller volume (weight) of trapping water. No satisfactory device of general application has yet been discovered by which this difficulty may be overcome with certainty and without entailing other effects equally to be feared. The present custom exacted or sanctioned by local Boards of Health is to carry a vent pipe from the upper bend of the trap to the open air, so that when the air of a pipe becomes rarefied, the balance shall be restored by admitting air through the vent pipe, leaving the water of the trap undisturbed. Theoretically, this practice has much to commend it; practically, it seems to me to have grave objections, which it will require our best endeavor to remove. Our best hope lies in the devising of some other means for securing a safe trap.

However completely we may succeed in preventing deposits in waste-pipes and drains, we cannot prevent the adhesion to their walls of more or less of the soapy, greasy, and slimy matters carried by their flow. With a perfect adjustment of diameters, and with the proper appliances for frequent flushing, such adhesions may be reduced to a minimum. However small the