The high-pressure cylinder, 17.5 inches in diameter, and the lowpressure cylinder, 36 inches in diameter, have each the same length of stroke as the pump-plunger, viz., 7 feet, and are placed close together at their lower end, under the beam-centre, with an outward inclination such that their pistons are connected with opposite ends of the beam, and move in opposite directions. The lower end of the high-pressure cylinder exhausts by a very short passage directly into the lower end of the low-pressure cylinder, under control of a single valve. The upper end of the high-pressure cylinder exhausts into the upper end of the low-pressure cylinder, through a passage about 4 feet in length, controlled by two valves, one quite close to each cylinder, so that the steam in this passage is retained as in a receiver, and the passage adds nothing to the clearance space. All the valves are gridiron slides; and those of steam admission to the high-pressure cylinder are automatically controlled by the governor, and are adjustable for various speeds. The air-pump is double acting, 11.25 inches in diameter, and 49.5 inches stroke, and is operated by a connecting-rod from the beam. The hot-well discharges into the pump-well, and the boiler feed-water is drawn from the hot-well by a donkey steam-pump. The water-pump is of the Thames-Ditton variety, and-plunger pump. -a bucket The pump-barrel is 26.1 inches in diameter, and the plunger 18.5 inches. The pump is vertical, and is under that end of the beam with which the low-pressure piston is connected. To the opposite end of the beam to which the high-pressure piston is connected, there is also attached a connecting-rod for driving the fly-wheel shaft by means of a 3.5 foot-crank. The fly-wheel is 26.5 feet in diameter, and weighs 24,000 pounds (about 103 tons). The beam is 14 feet long between centres, and weighs 9,500 pounds. The weight of the moving parts connected with the beam is 11,000 pounds. The several volumes of clearance and waste-room, in terms of the respective volumes swept through by the pistons, were: The passage between the cylinders is referred to the volume of the high-pressure cylinder. Boilers: two plain tubular boilers, shell 60 inches diameter, 16 feet long; with 77 flues, 3 inches outside diameter, 16 feet long; steam-drum 3 feet in diameter, 6 feet high; fire-grate 5 feet long, 5.5 feet wide. A test of this engine for duty and capacity was made on the 10th, 11th, and 12th of December, 1873, by a board of experts, consisting of William E. Worthen, James P. Kirkwood, Charles Hermany, Joseph P. Davis, and the writer. All usual and reasonable precautions were taken to avoid error and to insure substantial accuracy, and I see no reason to doubt the correctness of the results reached. The mean actual resistance acting against the pump-plunger was ascertained to be 72.41 pounds per square inch, to which was added, according to the terms of the contract and in conformity with a general custom, 1 pound per square inch, making 73.41 pounds. The trial was of 52 hours duration. The number of revolutions of the fly-wheel was recorded by a counter; fuel and water were carefully weighed and recorded, and plotted on a chart to check errors or omissions; and all circumstances affecting the result were taken into the account. Complete sets of indicator diagrams were taken at regular intervals, measured, tabulated, and computed. The result was 103,923,215 foot-pounds of work done by the engine for every 100 pounds of coal consumed in the furnaces. The subsequent record shows still better results. It appears from the annual reports of the Water Board, that during 6 years, 1877– 1882, the mean duty in foot-pounds calculated on all the coal consumed, including warming the engine-house while the pump was not running, was for each 100 pounds of coal, without deductions for ashes or residue, 90,212,158. Duty in foot-pounds calculated on all the coal burned, including warming, ashes and residue deducted, for each 100 pounds of combustible consumed, 103,513,392. Duty in foot-pounds calculated on all the coal consumed while actually pumping, without deduction for ashes and residue, for each 100 pounds of coal, 115,888,996. In these computations of duty, the one pound per square inch added, at the test, for estimated frictions and resistances in the suction-pipe and pump, was omitted, a difference of 1.38 per cent. PUMPING-ENGINE, LAWRENCE WATER-WORKS. This engine, also designed by Mr. E. D. Leavitt, jun., is similar to the Lynn engine last described, but is a little larger in all its dimensions, as will appear by the following table. Two of these engines are placed side by side, with a shaft and fly-wheel in common, so that they may be used singly or both together. Bottom and supplementary valves outside of main seat, inches 15.75 Volume of clearance and waste-room, in terms of volume swept Connecting-pipe between cylinders, referred to the high-pressure cylinder, .0992 35,900 Weight of beam, pins, and counter balance (14) tons), pounds Weight of main connecting-rod, beam to crank, pounds 3,800 45,250 The boilers were designed expressly for this engine. They have interior fire-boxes, divided by a "mid-feather" into two furnaces in each boiler; this mid-feather extends back 12 feet, beyond which a combustion-chamber extends 3 feet to the flue-sheet. The gaseous products of combustion pass from the combustionchamber through 80 flues 10 feet in length and 3 inches in diameter inside, and return beneath the boiler nearly to the ash-pit, where they pass downward, laterally, into a depressed flue leading to the chimney. A trial of this engine for duty and capacity was made May 2, to May 6, 1876, by a board of experts, consisting of William E. Worthen, Joseph P. Davis, and the writer, with an adequate number of trained assistants. The run of one engine by itself was divided into two periods of 22 hours and 35 hours respectively, with an interval of one hour and 34 minutes, caused by the accidental blowing-out of a pipe for attaching an indicator to the pump-chambers. A run of 34 hours was then made with the engines coupled together. Weir measurements were made of the quantity of water delivered to the reservoir; which showed a loss of action in the pumps, from their estimated capacity, of 5.2 per cent. The contract requirements were, for capacity, 2,000,000 gallons (of 231 cubic inches) in 10 hours, for each engine; and, for duty, 95,000,000 foot-pounds for every 100 pounds of best Cumberland (semi-bituminous) coal consumed in the furnaces. In determining the duty, the quantity of water pumped was to be ascertained by adding to the quantity measured at the weir, 5 per cent of the same for loss of action in the pump, - a quantity almost exactly coincident with the observed difference between the estimated and measured delivery. The resistance, or "lift," was to be ascertained by adding to the mean pressure observed in the rising main, at a point within 100 feet of the engine-house, the pressure corresponding to a water column equal in height to the vertical distance from the mean level of the water in the pump-well to the level of the pressure-gauge on the rising main, increased by 1 pound to compensate for resistances within the suction-pipe and pump. So determined, the dynamic lift was from 165 to 174 feet. The force-main was 30 inches in diameter, and 4,900 feet long; with branches from engines to main, 24 inches in diameter and 75 feet long. During the first and second tests, when one engine was run singly, both boilers were used; but the fire-grate area was reduced, by means of a wall of fire-brick built on the grates at the rear end, to an aggregate area of 47 square feet. When both engines were run, during the third test, the bricks were removed, and the aggregate area of the fire-grates was 56.67 square feet. Since the steam pressure and the speed of the engine were nearly constant, the state of the fire at any given time could be well inferred from the rate of firing during a certain period before and after that time, by inspection of a chart or diagram, on which intervals of time between firings were represented by abscissæ, and quantities of coal fired by ordinates; and the beginning and ending of the periods, of 22 hours and 35 hours for one engine, and of 34 hours for both engines, were determined in this manner. The water condensed from steam of boiler-pressure in the jackets of both cylinders of one engine was found, by measurement after the test was over, to be 338.85 pounds per hour, equivalent to the evaporation from feed-water temperature of 100° Fah. under mean |