the installation of sewage treatment works merely substitutes one nuisance for another.

Nuisances Caused by Trade Wastes.-It not infrequently happens that the greatest nuisance in streams is due not so much to domestic sewage as to the presence of trade wastes that may be discharged into the stream directly, or that may be allowed to flow into the stream through the sewers. For example, the discharge of spent dye liquors may color the water of a stream for many miles; petroleum wastes from gas works may cause iridescent films to form upon the surface of the water, producing an unsightly appearance and increasing the odor directly, as well as indirectly, by excluding air from the water; the acid iron wastes from galvanizing works may cause a rusty discolora

FIG. 126.-BURYING SLUDGE FROM HYDROLYTIC TANK AT HAMPTON, ENGLAND.

tion that not only imparts a brown color to the water, but paints the rocks and submerged stumps along the shores for many miles. When nuisances of this character arise it is wise and proper to install sewage clarification plants, and sometimes more elaborate works, for such nuisances cause real damage to property and to personal comfort. Trade waste pollution may interfere with the filtration of water even more than sewage itself. Illustrations of this are the paper-mill pollutions in New York State and the acid-iron wastes in Pennsylvania.

COÖPERATIVE SANITATION

What appears to be needed at the present time is some method of coöperation by which needed sanitary reforms can be brought about at least expense. It is unbusinesslike to compel the purification of the

sewage of a large upstream city in order to protect the water supply of a small city lower down, if pure water can be furnished the latter in some better and cheaper way. Legislation that clothes the State authorities with power to prevent the pollution of streams by sewage, but does not give them power to compel the purification of water or to control pollution by trade wastes, is unfortunate. It naturally leads to litigation rather than coöperation, and may retard rather than hasten necessary sanitary reforms. If our State authorities cannot be trusted in this matter it may be that a proper solution of the difficulty will be found in the establishment of district boards similar to those in England and Germany, such boards having jurisdiction over the limits of particular catchment areas. In some respects these natural hydrographic boundaries have advantages over artificial State boundaries. In the near future also our national government will doubtless take a hand in the matter. In whatever form the authority may be constituted the idea of coöperation should prevail, and ironclad rules against stream pollution should give way to a rational distribution of the burden of water purification and sewage treatment, and an equitable adjustment of cost made between the parties interested, thus decreasing the total expense of sanitary measures required and utilizing natural resources for the purification of sewage in water as far as this is safe.

If the system of water carriage of sewage continues in use the time will some day come when the sewage of all of our cities will be purified, partially or completely, and all surface water supplies filtered. It is proper to anticipate this consummation as far as our means permit, but meantime it is good business and sound common sense to spend our money first where it will go furthest and do the most good, building water filters and sewage treatment works, sometimes one, sometimes both, as they may be needed.

Adequate remedies against stream pollution from the standpoint of nuisance have been usually obtained by an appeal to the principles of common law. Cases involving bacterial pollution by sewage have been thus far too few to establish definite precedents. It will be interesting to see whether, in view of our increasing population, and especially the increasing growth of our cities, the courts will ultimately decide that the use of unfiltered river water as a source of water supply by riparian owners is a reasonable use of the water.

THE RURAL PROBLEM OF SEWAGE DISPOSAL

One of the most difficult problems of modern sanitation is to secure proper disposal of fecal matter in rural communities, at summer hotels, at temporary camps of laborers, at summer colonies at beach and mountain, and at individual houses in villages and on the farm. It is difficult

because the necessary structures are so small and simple that they have been thoughtlessly constructed, because adequate care of the processes is more or less disagreeable and therefore neglected, but chiefly because the inherent dangers have not been understood or appreciated.

FIG. 127.-CHEMICAL PRECIPITATION TANKS AT GLASGOW, SCOTLAND. LOWER END.

One of the most needed reforms, and one that is happily making progress, is that of the protected privy, that is, one where the fecal matter is received in a tight vault so constructed that the contents can

not be reached by flies, insects, rats, hens, or pigs, yet so ventilated as to prevent disagreeable odors and give opportunity for evaporation of liquids. This necessitates the liberal use of screens around the vault

and on the windows and doors, and the use of a self-closing cover for the seat. The privy vault may be constructed of concrete, with bottom and walls 3 inches to 6 inches in thickness, or the vault may be replaced with a tight, removable receptacle of metal or wood placed in a screened compartment. Properly constructed privies of this character may be located near dwellings, the only conditions being those controlling offensive odors, but this presupposes greater care than is ordinarily given to such matters. Preferably, therefore, they should be located at some reasonable distance from dwellings.

Privies that are not provided with water-tight vaults, but are so arranged that the fecal matter falls upon the soil, may be safe, so far as water pollution is concerned, if the soil is of proper character and

if the privy is sufficiently removed from the house well; but are undesirable for other reasons. No arbitrary rules as to the necessary minimum distance of a privy from a well can be laid down, as everything depends upon the character of the soil, the slope of the ground, the elevation of the natural ground water, and the draught of water from the well. A distance of at least 25 feet should be secured with sandy soils, whenever possible, and preferably 50 feet or more. With clay soils, liable to dry and crack, and in limestone regions, liable to contain crevices in the rock, leaching privies should not be used, as wells may be polluted 100 feet or even a mile or more away.

Cesspools are holes dug in the ground to receive not only fecal matter, but also, perhaps, sink wastes and water-closet discharges. They are often lined with loose stones to prevent caving, but this permits the liquids to leach into the soil. When the soil is sandy there is no objection to this method of disposal; in fact, it is like the method of sub

soil disposal previously described, except that the sewage is discharged into the soil below the depth where the soil bacteria are at work. This may be an important difference, however, and the oxidation of the dissolved organic matter proceeds by a slow and incomplete process. Leaching cesspools, however, should not be located near wells used for drinking water supplies. In sandy soils the danger of bacterial contamination is small if the distance is more than 25 feet, but, even so, the idea of infiltration of sewage into a well is repugnant, and often the water may be so tainted as to have a disagreeable odor, even when analysis shows it to be bacterially safe.

Ordinarily leaching cesspools should not be constructed in clay soils or in limestone regions, for they are liable to seriously pollute the

FIG. 130.-FILTER BED WITH SAND RIDGED FOR WINTER OPERATION AT BROCKTON, MASS. The ice sheet rests on the ridges. The photograph shows the accumulation of suspended matter during the winter.

ground water and are almost sure to overflow. If cesspools are necessary under such conditions they should be made water-tight and treated as septic tanks and the effluent taken care of by subsurface irrigation or some form of land treatment.

In cesspools the organic matter undergoes septic action and the amount of sludge that accumulates is often small. Nevertheless, cleaning is necessary at intervals in the case of all cesspools. The disposal of the contents is one of the most troublesome questions connected with this form of sewage disposal. The common method is to spread it upon the land as a topdressing. The work is apt to be done in the winter, when other farm work is not pressing, and not infrequently when the ground is frozen. Thus opportunity is given for fecal bacteria of human origin to be washed into a well or some public water supply. If spread