Cisterns should be water-tight, as cracks may admit polluted water from the ground. They should have water-tight covers to keep out dirt and also to prevent mosquitoes from breeding in them. After a dry spell the first washing from the roof should not be allowed to run into the cistern, as it contains dust and dirt which has accumulated on the roof since the last rain.

Sewage Disposal.

It is important that the discharges from the human body should be removed from the premises as speedily as possible. A water

LH•WILDER

FIG. 21.-The boxed receptacle. Flies are excluded by the
fly-tight box. Ventilation is provided by screened openings
in the sides of the box and in the lid. The hinged front
permits ready removal of the can for cleaning.
Such a
device is safe, sanitary, and convenient, and may be placed
in an existing privy house or in any suitable outbuilding.
(Original.)

closet connected with a sewer affords a means of disposing of human waste which has many advantages over the privy or cesspool. As the former is usually placed in a heated room a person using it does not become chilled, as is frequently the case when he has to go outside to a privy. The sewer removes the material to a distance and prevents contamination of the soil and its conveyance by flies to food. It is advisable that all buildings be provided with a water-carriage system, but it is especially important that this be the case in towns having a population of over 3,000.

In thickly settled sections of the country the sewage should be given some preliminary treatment to render it less dangerous before

it is emptied into a river or lake. There are a number of ways of doing this, among which may be mentioned the spreading of the sewage over the surface of the ground at a location which will not render it objectionable to the inhabitants of the city; it may also be treated by means of a sand filter in the same manner as water; or if the ground is of sandy formation it can be spread upon the ground and allowed to soak into the soil; trickling filters may be used by which means the liquid sewage is sprayed over rocks and thoroughly exposed to the air, the purified sewage running off through drains at the bottom of the pile of rock. When there is a large quantity of trade waste in the sewage, sedimentation may often have to be used, lime, copperas, or alum being employed to hasten the precipitation. Large settling tanks may be employed in which the sewage is allowed to remain from 8 to 24 hours, during which

time some of the solid substances undergo liquefaction. From this tank the liquid sewage flows over rock, laths, or other rough surfaces whereby it comes in contact with the air. Sewage may also be disinfected, after it has been subjected to the

action of the air, by the addition of bleaching powder, but this is not often necessary, as it is not intended to free it entirely of bacteria but only of a large percentage.

The efficiency of the various methods described above is given by Whipple as follows:

Sewer air is objectionable in the same manner as any impure air would be, but the old idea that many diseases are contracted through sewer air is no longer considered tenable as the danger of contracting these diseases by breathing this air is extremely small. Sewer pipes leading into a house should have a trap at the connection of the house drain with the street, and in such cases it is questionable whether it is necessary to have other traps in the building. The

system of traps and vents now in use is unnecessary, and the plumbing of the future should be developed along simpler lines, thereby saving expense to the builder without loss in efficiency.

Privies.

In rural districts and in small towns which have no water-carriage system, privies should be used to dispose of the discharges from the human body. If a privy is properly constructed, intelligently used by all members of the family, kept in repair, and the contents removed at regular intervals and deposited in a safe place, the water supply will not be contaminated and flies and other insects will not carry disease to persons living in the home or in the neighborhood. The privy should be screened, should be provided with an automatically closing lid over the opening in the seat and should have a watertight receptacle to receive the discharges, arranged so as to be easily removed or cleaned.

The following types of privies described in the publications of the Public Health Service conform to the principles of sanitation and have proved in actual use to be practical.

Covered can. This is simply a can with a closely fitted wooden top, having a suitable hole covered by a hinged screened lid.

Boxed can. In this type the receptable is inclosed in a box with a suitable hole in the top, covered by a lid. The top or side should be hinged to permit the taking out of the receptacle for emptying. The box should be somewhat larger than the receptacle in order that its removal may be easily effected. The receptacle may be placed in the back of a privy, if it is so desired, and the space around it boxed up with a screen door at the back. Such an arrangement keeps the discharges off the ground and prevents flies from breeding in or feeding on them. The box should be well ventilated either by screened openings or by a ventilating flue to remove objectionable odors. Lime, dry earth, and ashes may also be mixed with the feces for this purpose, a cupful being placed on each stool immediately after it is deposited.

The L. R. S. privy.1—If human excreta are permitted to undergo natural fermentation, the solid matter becomes liquefied and a considerable proportion of the excrement and urine is carried away by evaporation and gas formation. Thus the labor and cost of disposing of the matter may be lessened. These principles are applied in the L. R. S. privy. (Figs. 26 and 28.)

1 Lumsden, Roberts, and Stiles: "Preliminary note on a simple and inexpensive apparatus for use in the safe disposal of night soil." Public Health Reports 1910, Nov. 11, v. 25 (45), pp. 1623-1629. Stiles and Lumsden: The Sanitary Privy. Farmers' Bulletin 463 (U. S. Department of Agriculture), pp. 17-21. Lumsden: Public Health Bulletin No. 51, pp. 46-49.

FIG. 23.-Front view or removable-receptable privy. (Stiles, 1910.)

This apparatus consists of the following parts:

(1) A water-tight tank, barrel, or other container, to receive and liquefy the excreta.

(2) A covered water-tight can, pot, barrel, or other vessel. to receive the effluent or outflow.

FIG. 24.-Rear and side view of a removable-receptacle sanitary privy. (Stiles, 1910.)

(3) A connecting pipe about 2 inches in diameter, about 12 inches long, and provided with an open T at one end, both openings of the T being covered with wire screens.

(4) A tight box, preferably zinc lined, which fits tightly on the top of the liquefying barrel. It is provided with an opening on top for the seat which has an automatically closing lid.