The force main has proved to be sufficient for all need since our last report; but we see no reason to alter our judgment that it will be wise to construct a second line.

Slight repairs only, occasioned by the action of the frost, have been necessary at the reservoir, which, with the grounds about it, are in good condition. The roadway over the force main will be constructed by the Board as soon as they have the authority of all parties interested in the land. Its construction will be a benefit in appearance to the water works, and, in our judgment, of decided pecuniary advantage to abuttors.

SUPPLY MAINS AND DISTRIBUTION PIPES.

The thirty and twenty-four inch supply mains have required but very little attention during the period of this report, and we know of no reason why they may not be considered in good condition. Authority having been granted by the Board to the City of Somerville, a twelve-inch main pipe, connecting with one of the supply mains at the reservoir, has been laid by said city through a street in the grounds of Tufts College, called Packard street, to Broadway, in Somerville. By means of this pipe the westerly portion of the City of Somerville is more satisfactorily supplied with water, both for domestic purposes and for the extinguishment of fire. The order of the City Council of July, 1874, authorizing the Board to lay a sixteen-inch castiron main from Canal street to City square, was carried into effect by a contract with Mr. George H. Norman, who did the work in a prompt and faithful manner, for the sum of thirteen thousand seven hundred and fifty dollars.

The length and sizes of cast-iron and cement pipes laid in the streets during the year are given in the report of the Superintendent. Wrought-iron and cement pipes, if thoroughly filled and carefully laid in good cement, are durable

and satisfactory; but when they have been carelessly laid they cause much trouble and expense. A good deal of work will be necessary during the next year, in relaying many pipes where they have been put down before in a careless and improper manner.

The long-continued and extreme cold weather during the winter filled the ground with frost to a very unusual depth, and the number of main and service pipes frozen up far exceeded that of any other winter since the introduction of the water. The increased amount of the laborers' pay-roll, during the winter and spring months, will indicate the expense which such a state of things occasioned,

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SUPPLY OF WATER.

Up to the first of September, 1874, the supply of water was sufficient to keep the lake full, the level at that time being 10,5 feet above the bottom of the conduit; but from that time to January 1, 1875, it gradually lowered until it was only 5 feet above the bottom of the conduit,— a lower point than it had ever reached. The drought continuing, its effects were more and more manifest, and on the 8th of January, the Board, thinking it would be imprudent and dangerous to delay any longer, gave orders for the construction of a pump to raise the water into the conduit, and the purchase of an engine to work it. The consumption and waste of water was all the time on the increase, and in two weeks in the month of February it averaged over twelve million gallous daily. The extreme cold weather made frozen pipes or running water the alternative, and water-takers lessened their own anxiety by increasing that of the Board. The trouble was checked somewhat by the circulation of printed notices, stating the condition of the lake, and giving warning as to the effect of the great waste; but decided relief came only with milder weather. The pump for filling

the conduit was completed on the 3d of February, but a thaw with rain commenced on the 4th, which raised the water enough to make its use at that time unnecessary. On the 18th it was put in motion, but after several hours' work, it was stopped by an accident to the machinery, and by the time the damage was repaired a decided change in the weather had taken place. Rain and mild weather soon filled up the lake, and did away with the necessity of pumping into the conduit. The expense of fitting up the pump with the machinery necessary to work it was quite considerable ($5,195.42); but, with the state of things existing at the time, it could not be avoided. We had previously made arrangements for the use of the water in the mill-ponds above, and had exhausted their supply. There seemed to be no end to the drought and excessive cold, and the consumption was all the time on the increase. When the change did take place, and the thaw came, it showed, not only how speedily the lake could be filled, but the certainty of a large supply from the Mystic basin in all ordinary seasons.

WATER-SHED, CAPACITY OF LAKE, ETC.

In April, 1874, the City Engineer reported the result of the survey and estimate of the area of the water-shed of the Mystic upper lake to be 27.75 square miles, which settled a matter about which there had been some controversy. In the month of July, 1874, some experiments were made, under the direction of the City Engineer, to measure the flow of Mystic lake, or to ascertain the capacity of the Mystic water-basin. The experiments were made by Mr. A. Fteley, and the Mystic Water Board employed Mr. Thomas Doane to witness and take part in them. The year 1871 was taken as the year of smallest yield of water, concerning which there was sufficient data that could be used for calculating its quantity with any reasonable degree of accuracy. Most of

the observations of that year had been taken by Mr. Symmes, Assistant Superintendent of the Mystic Water Works; and enough experiments on the flow of water were tried, to calculate from these observations, and the result given for each month in the year in the following table :

Product of Water from the Upper Mystic Water Basin for the Year 1871.

From this it will be seen that in a year like 1871, the Mystic basin can be depended upon for a daily supply of 17,065,313 gallons. But to do this, additional storage basins must be constructed, as the quantity wasted over the dam was 58 per cent. of the whole yield of the lake. In the result of the experiments made, the City Engineer and Mr. Doane

were agreed; and we think their conclusions can and should be relied on in estimating the value of the water supply from this source, or in making calculations for increased storage capacity, or other improvements in the Mystic waterbasin.

QUALITY OF THE WATER.

On the 30th of December, 1873, Prof. E. N. Hosford, of Cambridge, made a report to the Cochituate Water Board, on the purity of Mystic water, which was printed in City Document No. 134 of that year, with the report of Messrs. Kirkwood and Francis, on the question whether the Mystic could be relied upon as a source of supply, etc., etc. In that report, Prof. H. says, "Of the fitness of the Mystic water for boiler use, there seems to be no doubt; of its fitness for domestic use in the laundry, it is substantially what it was at the time of its introduction, a remarkably soft water; of its salubrity as a drinking-water, it will compare well with the best water in use for city supply. It has experienced no appreciable detorioration since its introduction ;" and he adds, "If the contribution from factories and domestic sewage continue to be no greater than they are now, and have been hitherto, and the volume of water remains the same, the selfpurifying power of the water will be adequate to maintain its salubrity. In case this factory drainage and domestic sewage are steadily increased, and especially if the water from any cause be diverted or diminished, a time will come when the self-purifying power of the water will be overborne. When such time does come, independent drainage for the factories and domestic sewage to a point below the entrance to the aqueduct will restore the balance." In giving his opinion, he says, "I submit the results of analysis, and the influences that seem to flow from them;" and we may add that similar results have been shown in the many analyses which have been made from time to time, by different but eminent chemists, for this Board. Messrs. Kirkwood and