To insure a constant and due quantity, Mr. Watt contrived a simple plan for low pressure stationary engines, by which the engine is made to supply the boiler. One of these is in use at the Globe-mill Cotton-works, near Philadelphia. Mr. Doolittle of Vermont has invented another, and described it in the Journal of the Franklin Institute, vol. iv. This feeder, like that of Mr. Watts', has a regulating cock, or valve, between the forcing pump and boiler, and the pump must continually urge towards the boiler its maximum quantity of water, whether the boiler is in a state to receive it or not. Mr. Charles l'otts of Phil adelphia, has recently taken out a patent for an inven tion to effect the same object; an account of it may be found in the Franklin Journal for 1830, vol. vi. pp. 42 and 327, illustrated by a plate. His object is to secure the self-action of the supply pump, by the falling and rising of a float in the boiler. In the same work and volume Mr.Ewbank of the state of New York has proposed another plan, and with the excep tion of this principle, somewhat on that of Air. Potts; who announces that Messrs. Hush and \luhlenberg, of Philadelphia, will attach his apparatus to engines. In vol. vii. p. 183, is a specification of another patent granted to John S. Williams, of Kentucky, for the same object, with a cut illustrative of the apparatus. Finally, Mr. Farcv describes at length. and figures a contrivance wherewith the boiler will always feed itself as fast as its evaporation requires; the water being admitted by a feeding valve, which is opened by a float on the surface of the water in the boiler. This is the mode adopted in England. With all these contrivances to prevent a common cause of explosion, no admissible excuse can be offered by proprietors of boats, for deaths which may take place for want of them.
6. To lessen Sediment in Boilers. In the collieries in Scotland, where steam engines are applied to the drawing off the water in mines, the earthy sediment has been found very troublesome, but its deposition is prevented by the simple ex pedient of throwing a bushel of comings into the boiler once a week. This substance is the radicles of barley produced in the process of malting, which are separated before the malt is sent to market. Mr. Bald of Alloa says,11 the effect is immediate when the steam is again raised. When sulphate of lime (gypsum) is held in solution by the water.
they use peat earth in its natural plastic state. From Silliman's Journal vol. vii., it appears from a state ment of Professor Griscom, of New York, that potatoes have long been used in the United States for the same purpose. Arago says that they answer even when the deposit is saline, by which itis presumed, he alludes to the contents of salt water. The dif fusion of the starchy feculm through the water forms a viscid liquid, which envelopes the solid matters of the water, and keeps them suspended, and prevents their cohesion. After a month's service, the boiler is emptied.
To prevent the formation of sediment in the boiler, one of the experienced captains on the Delaware says, that the water should be changed while the boat is under way, as the sediment would thus be made to flow out of the legs of the boiler and space in front; and to determine whether the force pump supplies as much as is let off, and the flues are covered, one guage cock should be kept open. The superb boat, Robert Morris of Philadelphia, the works of which were made by Mr. Holloway, has not only a man-hole to clean the boiler, but additional facilities to remove sediment, consisting of a vent hole or tap in each of the three front legs of the boiler, a hand hole covered with a screw plate, in the middle front leg; two hand holes, one on each side of the further end of the boiler, and another hand hole on the side of the boiler, opposite the bridge wall.
The apparatus adopted at the mint, and formerly referred to, to lessen the deposit in a stationary en gine, is as follows.
The operations of the coinage in the Mint at Phila delphia are effected with the aid of one of Oliver Evans' high pressure engines. For sometime after its erection, the grease from the cylinder, being carried into the boiler with the water of the condensed steam, united with the earth in the water of the boiler, and forming a hard sediment on the bottom plate caused it to burn out. The boiler being mended required
to be cleansed once a month. To lessen this trouble, and prevent the frequent suspension of the work, Mr. Eckfeldt, chief coiner, some years since adopted the following plan. He surrounded the escape pipe with a copper cylinder twelve inches in diameter, and containing thirty gallons of water, which is let into it by means of a pipe lying on the side and near the top of the cylinder, and kept constantly hot by the i steam in the pipe. The steam passes into a cast iron reservoir; the portion of it condensed flows into a sink through a hole in the side of the reservoir, with the filth from the cylinder, while the uncondensed portion of the steam is conveyed up a pipe fixed in the top of the reservoir, and leading into a chim ney. When the boiler requires replenishing, the hot water in the cylinder is let into a reservoir, and forced into the boiler. Thus, while there is great economy in supplying the boiler with hot, instead of cold water, the deposition of the hard crust on the inside of the bottom plate is greatly lessened, and no sediment precipitates but that which is formed from the earth contained in the water, with which the copper cylin der is filled. This is so trifling, that th' boiler does not require cleansing oftener than once in three or four months. From the great head on the Schuylkill water, the workmen are enabled to draw off the heated contents of the cylinder, by merely fixing a pipe to the aperture in its top, intended for the admission of the cold water. This heated water being in perpetual re quisition for various purposes about the establish ment, the constant supply of it is found a great conve nience. A safety valve in the cylinder prevents all danger from the too great accumulation of steam in it. 7. Safety Valves. Under the tenth head of the causes of explosions, six particulars are enumerated, all tending, to disappoint the expectations of security from safety valves; and in the commentary uponthem, some facts in illustration are given. It seems astonishing that an er ror should be committed as to their diameter, and yet such is said by a careful and experienced steam-boat navigator to be often the fact. As the rules for their construction are well understood, and fully laid down, it is criminal for those who undertake to make an engine, not to avail themselves of the important know ledge in their power. This may be obtained by con sulting Mr. Farey's large work, or that of Mr. Ren wick, p. 86. The object of the present article is not to enter in the minute details of the mechanism of en gines, but to point out the causes of the dreadful ex plosions that have taken place, and to suggest the general means of preventing them. The adhesion of the disk should be constantly guarded against; in the case of the Legislator already noticed, the vigi lance of the engineer, and his prompt attention, probably prevented the occurrence of a most serious explosion from this cause. To prevent the possi bility of art adhesion, Mr. Matisdlay, an experienced worker of steam in England, placed near his boilers a cord within reach of the fireman, by which he could raise the safety valve from time to time. But this is not enough. Supposing that the valves are properly constructed, it has often been recommended to have two to every boiler, one under the control of the fire man, to be used whenever the steam is to be let off; the other to be inclosed by a grated box, of which the engineer, or captain of the boat, proprietor, or super intendant of the engine, should have the key. Arago says, that in France a royal ordinance makes this precaution absolutely essential; and the government of the United States, or the State Governments, should follow the wise example. The preservation of 1500 lives, which may again be lost in the course of a few years, by inattention to the subject of steam-boats, is certainly of more importance than the inspection of hog's-lard and butter for exportation, for which strict laws are in force.