sterile as regards the presence of living organisms, as the re-agent which is formed by the chemicals is completely destructive to organic life. I have witnessed a trial of the process at the Wimbledon Sewage Works, where herring-brine is used, which is mixed with milk of lime and evolves a soluble gaseous re-agent, having a briny odor. This, when applied to the sewage, produces rapid deodorization and deposition of flocculent matter. Dr. E. Klein, F.R.S., has examined the process and confirms the sterilizing influence of the effluent which is claimed.”

II. In the Irrigating Process, the sewage is applied in as fresh a state as possible to the land, with a view to cultivation and some profit in farming. There is, of course, filtration through the soil, but it is distinguished from other methods because dependence is placed upon. the power of growing vegetation, and the irrigation or application of the sewage is not made subservient to the rules and methods which obtain in the Intermittent Filtration system.

III. Intermittent Filtration was introduced by Dr. Frankland, but has undergone many modifications. The reports of the Massachusetts Board of Health, 1888 and 1889, contain much of value as to it because of some valuable experiments conducted at the Experimental Station of the Board. The full report will be completed this year. The two leading new facts which seem to be brought out by these experiments are these:

First. "Sewage can be more efficiently filtered through open sand than through sand covered with soil, and the maximum quantity of sewage can be purified when the upper layers of the filter are composed of open sand through which the sewage will rapidly disappear, and into which the finely-comminuted particles of suspended matter will be drawn by the force of the down-flowing currents. The daily application will sink into such a filter in a few minutes, leaving room for air to enter and come in contact with the thin laminæ of liquid covering the particles of sand. A filter so constructed, it may be remarked, is quite different from those ordinarily used, in which fine sand or loam is placed at the top with coarse material beneath. In constructing filter areas in accordance with the new views which we derive from these experiments, we would, therefore, reverse the old process, using fine material at the bottom and coarse at the top. In

a practical way, we would, under ordinary circumstances, strip off the first foot or so of surface-soil and replace it with coarse sand. The additional expense imposed in the construction of the filtration areas by making the upper foot in depth of coarse sand amounts to from $300 to $400 per acre. There comes from this, however, a decided increase in the efficiency of the filtration area, and consequently a given area so prepared will do more in the way of purification than areas not so prepared. This increased efficiency of area leads again to reduction of annual expense, inasmuch as a considerably less number of men are required to attend to 100 acres, the amount estimated in the report. With such filtration areas thoroughly underdrained to the depth of five or six feet, the sewage of 1,000 persons per acre may be efficiently purified with proper management, for all time to come. I say for all time to come, because we now know definitely that the filtration area is not a mere straining arrangement, but that it is, on the contrary, an appliance for cultivating the microbe of nitrification, the recent studies upon nitrification having confirmed the view that the destruction of organic matter by nitrification is a biological process purely, and not, as has been ordinarily considered, a chemical process at all. The experiments show further, that not only is the nitrification due to living organisms, but that the microbes are confined to the surface-soil and are found only rarely three feet below the surface." Such a filtering field is said to be entirely devoid of smell.

The second idea illustrated is, "The fact that there is a relation between the quality of the filtering material and the amount of sewage of a given composition to be applied. Thus, if less than a proper amount of sewage is applied to a given area of a given material, less perfect purification will be obtained than if the larger quantity which the given material is capable of handling is applied. From whence it clearly results that undoubtedly many of the foreign. experiments in this direction have been failures from lack of a clear understanding on the part of the experimenters of the necessity of applying a certain definite amount of sewage to a given area, in order to develop the maximum nitrifying power of the filtering material.”

An excellent brief report on these various systems, by Engineer Geo. W. Rafter, of Rochester, N. Y., as made to that city in May, 1890, will well repay perusal.

USE OF THE SPECTROSCOPE FOR DETERMINING WHETHER CESSPOOLS, ETC., CONNECT WITH WELLS.

Prof. L. I. Blake, of Kansas, has been able to detect the presence of sewage in wells by a method which is thus described by him :

"It is familiar to all that a glass prism will separate a ray of sunlight into the seven colors of the spectrum. If the ray comes from a metal which is vaporized in a hot, colorless flame, as in a Bunsen gas flame, the spectrum no longer consists of all the colors, but of one or more bright bands, characterized by their color and position in the spectrum.

"Thus, sodium gives a bright yellow band, which is in the position of the yellow in a Swiss spectrum, while calcium gives two, a red and green band, in their proper places. The spectroscope, which is essentially a glass prism, and a small telescope to observe the spectrum with, can thus detect by their characteristic bands the presence of substances which can be volatilized in a colorless flame.

"Further, there can be no mistake, for no two metals give the same bands. The question arises, can small quantities of the substances in solutions be thus detected? Prof. Schellen asserts the sure and easy determination of sodium, when less than the 180,000,000th part of a grain is present, and of lithium when less than 40,000,000th part of a grain. The delicacy of the spectroscopic tests thus exceeds the chemical Indeed, by the spectroscope several new metals, as thallium, rubidium, caseium and iridium, have been discovered. For the purpose on hand, then, the spectroscope provides an exceedingly simple method.

"A solution of carbonate or chloride of lithium, an ounce to a quart of water, was poured into the suspected sources of pollution in the neighborhood of a well, and after a week or so some of the wellwater was examined in the spectroscope. Lithium gives one bright red band toward the remote red end of the spectrum. It is impossible to mistake it, even if the solution holds less than one part in one million. The sensitiveness of the test is greatly increased by boiling down the water to be examined, say a quart to half an ounce. platinum wire is dipped into the water thus prepared, and then held in the flame of a Bunsen burner.

A

"Nine wells were examined, situated back of the blocks on the principal street in Lawrence. These wells are located, as regards stables, out-houses, &c., about as is customary in small cities, and their waters are used quite generally for drinking purposes by the families in the blocks. The test showed direct communication with a privy, thirty feet distant, into one of the wells."

STOPPAGE OF DRAIN-PIPES, GREASE AND GREASE TANKS.

Much risk and annoyance are occasioned by the stoppage of housepipes, either inside the house or between it and their connection with the cesspool or sewer. Occasionally, in small pipes, this happens from freezing, by reason of the exposure of the outside drain, and a dribbling or intermittent flow. This is rare, and the only remedy is the usual one, of thawing out. Oftener, something gets fast in a small pipe, and so collects around it material which clogs the pipe. Plumbers now have instruments for the dislodgment of small stoppages between traps. Sometimes a strong solution of caustic potash, such as is used in making soap, will dissolve out the obstruction. Often the trap itself has gathering in it sediment that serves to fill up the pipe where the flow is not rapid enough to clear it. Hence, those traps are valuable which have a screw fixture at the bottom, so that the seal can be opened and cleansed. But the most prolific causeof stoppage is the accumulation of grease in the pipes. As to this, and the remedy, we cannot do better than to quote from E. S. Philbrick, C.E., in "American Sanitary Engineering: '

"The grease comes from the washing of dishes in kitchen sinks, which goes down the wastes, mixed with warm water, in a fluid state. It soon becomes chilled in cool weather, and adheres to the sides of the drain, where it accumulates continually, till sometimes filling the pipes for long distances. If the drain has a very rapid descent, the flow of water may sometimes prevent this accumulation, but otherwise some provision is needed for intercepting the grease in a small tank. The nearer this tank is to the sink the better, to guard against the choking of the pipe above the tank. Where the sinks are located against the outer walls of the house, the tank is best placed outside the walls, where the grease can be removed without creating a nuisance in the house. Such a tank is shown in this diagram, built of brick and hydraulic cement, plastered smoothly inside.

"The inlet and outlet-pipes are so located as to each other as that the outflow starts from below when the level of liquid reaches a certain point, and so the grease has time to congeal and separate.

"For small and medium houses, this tank should be at least three feet long on the inside, and about two feet wide, with rounded corners. The outlet should be made with a bent-joint pipe dipping under the water, so that the grease, while floating on the surface, will not be drawn into it. The inlet should be at least six inches higher than the outlet, so as not to be obstructed by the accumulation of grease, which takes place in the form of a thick scum on the water.

It is also best to allow about a foot below the mouth of the outlet in the clear, for the accumulation of sand and other solid matter which is heavier than water. A man-hole cover is placed on the top, through which the grease may be removed as often as occasion may require. The soil-pipes from water-closets should never discharge into this receptacle. It should be so arranged upon the branch leading from the kitchen and pantry sinks only, having its outlet connected with the main drain where convenient. If the sink is not situated near enough to the outside of the house to allow this grease tank to be constructed outside the walls, it can be made in the cellar or basement, of wood, and lined with heavy lead. In such cases the grease does not cool so readily as on the outside, and if the tank is not of a liberal size, the grease is liable to pass through before being separated from the water. Whenever the drains become choked with grease, if the pipe is accessible, it can be cleared by pouring hot water over the outside in a small stream for half an hour or less. This heats up the whole contents, and the softened grease then passes along with the water that is applied outside. But the better way is to catch the grease before it gets into the pipes. If once allowed to coat the inner walls of the drains, much trouble will ensue."