MECHANICS AND USEFUL ARTS. 45 



conical holes five-eighths of an inch diameter, and filled with fusible metal 

 plugs, simply driven in. By this arrangement should the water fall below the 

 upper surface of the pipe, the fusible plugs being constantly exposed to the 

 current of the heated gases, passing through it immediately melt, and thus 

 preserve the boiler from injury. The pipe could be made of wrought or 

 cast-iron, brass, or copper, but the author preferred them, of wrought iron 

 or malleable cast iron. Before venturing to bring the plan before the public, 

 he made several experiments upon one of his own boilers. At the time the 

 experiments took place, the pressure of the steam averaged from forty to 

 forty-five pounds the square inch, the water then, being at its proper working 

 height, that is to say, three or four inches above the covering in, or top of 

 the side flues. To facilitate the experiment, the water was blown off until 

 its level was not more than one fourth of an inch above the top of the pipe. 

 Instructions were then given to the stoker, to fire up, and increase the 

 steam pressure, with a view to evaporate the water as quick as possible, 

 and reduce it below the proper level. Through a spy hole made in the 

 brickwork the action of the fire could be distinctly observed playing upon 

 the plugs until they melted out. It was subsequently found that three of 

 the plugs had given way, thus relieving the boiler from steam pressure, 

 and gradually putting out the fire, while a sufficient quantity of water was 

 reserved to enable the stroker to recommence firing, with but little delay of 

 the replacing of the plugs. 



ENGINES OF THE BROOKLYN WATERWORKS. 



The largest pumping engines in the United States, and, with few excep- 

 tions, in the world, are those in course of construction for the Brooklyn 

 Water Works by Messrs. Woodruff and Beach of Hartford, Conn. Each 

 of the two engines will lift 10,000,000 gallons to an average height of 165 

 feet per day of sixteen hours, through a tube thirty six inches in diameter 

 and about 3,300 feet long. 



The conduit of the Brooklyn Water Department is situated some 130 

 feet below the great distributing reservoir, and powerful engines are ne- 

 cessarily required to raise the water. The two machines now in course of 

 construction are double-acting fly-wheel engines of ten feet stroke and eighty 

 inch bore, each working two pumps of fifty-four inch bore and thirty six inch 

 effective stroke, by spiral cams. 



This is a modification of the Hartford pumping engine, built by Messrs. 

 Woodruff and Beach, in which the fly-wheel shafts gear, with two pump- 

 shafts, each driving two pumps and reducing their speed to one third that 

 of the fly-wheel shaft. The four pumps are each fitted with double pistons, 

 worked by the cams, alternately toward and from each other, with a lap on 

 the upper and lower centres, so that the water is lifted without changing its 

 direction, as in other double-acting pumps. In the Brooklyn engines, only 

 one pair of pumps will be used for each, the piston of one working its 

 charge through the other, the effective stroke of each being thirty six inches 

 with forty-two inch travel, and the cams being connected directly to the fly- 

 wheel shaft. Double-beat valves are also to be used 



