tion is on the outskirts of the territory to be supplied, or is not sufficiently central for an economical system of distribution; it would require the water to be brought to it in pipes, at great cost, and a considerable loss of head; and it is so low that a pressure of over thirty pounds per square inch is created on the suction side of the pump piston, which produces a harsh action of the machinery, and to some extent impairs its efficiency.

"The new works should be of a kind that have reservoirs as centres for the distributing pipe systems.

"The area to be supplied consists of various districts, more or less isolated, for each of which there should be, as a matter of economy, a distinct system of distribution, and to secure to them an uninterrupted supply under a nearly constant head, and that the supply mains leading to the districts may be of the minimum size and cost, reservoirs should be established at convenient points.

"The existing high-service works were designed to supply a limited area only, and were not constructed upon a scale to meet the requirements of the large territory even now depending upon them, much less to provide for further extensions due to annexation.

"The pumping machinery consists of two engines, each of a capacity to pump 2,400,000 gallons in twenty-four hours, when making thirty-five revolutions per minute. These engines are supplied from a single line of pipes, sixteen inches in diameter, under a head which gives about thirty-three pounds of pressure upon the pump piston; and to enable the latter to work at the guaranteed speed, it was found necessary to connect the supply line with a large air-chamber. The pump force mains, immediately after leaving the engine building, are united by a Y branch into a single line of pipes, sixteen inches in diameter, which leads to the stand-tower on Fort Hill, and is about 2,500 feet long. On account of the connection of the engines, through the

supply and force

pipes, they are found to react, one upon the other, when working together, and it is not considered safe to thus use them at a speed which will give a much greater discharge of water than will one engine alone, run at its safe maximum velocity.

"As the capacity of one engine is less than that of four steam fire-engines, it will be seen that the power to supply water in times of fire is very inadequate. The laying of independent supply and force mains would nearly double the available capacity of the engines for emergencies, and would provide a safeguard against stopping the supply in case of a burst.

"Under the existing arrangement, a burst in either the supply or force line would deprive the high-service district of water until repairs could be made, and should such an accident occur during a fire, the consequences would be serious.

The steam parts of the engines having sufficient power to drive larger pumps than are now in use, it has been suggested that these pumps may be replaced by others of greater capacity. Such a change would be somewhat of an experiment, and unless much more valve area, or a better passageway for the water than the pumps now have, can in some way be provided, I doubt whether it would effect much gain. But even if it can be successfully made, sufficient pumping capacity would not be secured, under adverse circumstances,

such as one engine being under repair, or dismantled for cleaning, to meet the demand for water in case of a large fire within the high-service limits.

"The pumps now in use are fourteen inches in diameter, and have a stroke of three feet, and a capacity of forty-eight gallons per revolution of the engine. The diameter that has been proposed for the new pumps, to replace the old ones, is sixteen inches, which gives a capacity of sixty-two gallons per revolution, or 130,000 gallons per hour, when the engine is

running at its guaranteed speed of thirty-five revolutions per minute.

"The average maximum hourly consumption of each day, during the coming season, will not fall short of half of this amount, or say 65,000 gallons, and will much exceed it in the following years. If, in addition to this consumption, there be required a supply for six steam fire-engines (which number the Chief Engineer of the Fire Department says should be provided for), each throwing 450 gallons per minute (the average amount), the delivery must be at the rate of 227,000 gallons per hour.

Both engines, running together, would meet such a demand, but perfect safety is not secured when it is necessary that all the machinery shall be put in operation to meet an emergency that is likely to arise without previous warning. There should always be a reserve engine, to admit of repairs and cleaning at any time. Setting aside the domestic consumption, one engine alone, even if provided with a sixteeninch pump, could not supply more than five fire-engines; it is clear, therefore, that, to secure proper safety, some special provision must be made to keep up the supply in times of large fires.

This provision may consist either in the erection of a third engine, or in the building of a reservoir and connecting it with the stand-pipe.

"If the engine be erected, it should have a capacity to pump about five million gallons per day, that when in use it alone may furnish all the water required both for extinguishing fires and for domestic supply. Owing to the comparatively small draft at night, such an engine would be larger than can now be conveniently used for keeping up the daily supply; but, for the present, it can be kept in readiness for service in emergencies, and, as the consumption increases, can be gradually brought into more constant use.

"There are now two boilers in service, each rated at one hun

dred horse-power, or of sufficient capacity to drive the new engine; nevertheless, a third boiler, of somewhat greater power, should be provided.

"The arrangement proposed is, then, two small engines (the existing ones), each of a maximum capacity of about two and a half million gallons per day, and a new engine and boiler having a capacity of about five million gallons, and supply and force mains twenty-four inches in diameter.

"The two small engines, when run together, or the large engine alone, will furnish any supply that is likely to be required from them within the next few years.

The chief objection to this plan is, that a large expenditure will be necessary for machinery, buildings, mains, etc., which probably will be thrown out of use at the end of a few years.

୧୯

A reservoir can be built on Parker's Hill, at an elevation that will give sufficient head on the high-service pipes, or with a water-surface about two hundred feet above tidemarsh level.

"If this reservoir be connected with the stand-tower on Fort Hill, it will be put in good communication with the highservice distributing system, and will instantly respond to any demand for a sudden increase of supply.

"The ratio between the average and maximum quantities of water pumped in an hour, during each month, has varied in

143

255'

the past year from 10 to 100, as shown in the following table:

“Table showing the average and maximum quantities of water pumped in an hour, and the ratios between them, for each month of 1872.

"From the above it will be seen, that an engine which has to vary its speed as the consumption of water varies, is required to be about double the capacity of one doing the same work under a uniform speed; that is to say, to furnish a given supply, an engine pumping into a stand-pipe should have twice the capacity of one pumping into a reservoir.

"Hence it follows that the building of a reservoir, besides insuring an ample supply of water for the extinguishment of fires, would, by virtually doubling the pumping capacity, be equivalent to the addition of a new engine having twice the power of each of the existing ones.

"If it be built to serve a temporary purpose only, its connection with the stand-tower may be made with a line of twenty-inch pipes, but as its proposed location is the proper one for one of the auxiliary reservoirs of the future highservice system, its pipe connections should be proportioned