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'aida es 238 et Ho i MARINE REVIEW. Ae in the cylinder when cut off from the boiler, and proposed it in a letter to Dr. Small in 1769 (see Farey's "Treatise on the Steam Engine," Lon- don, 1827, page 339). He was also the first to put the idea in operation which he did at the Shadwell water works in 1778 (Farey, page 341). He patented the application of this principle in his third patent, dated March 12, 1782, and in the specification and drawing clearly and beautifully illus- trated by a diagram the principle of expansion (see Farey, page 347). He thereafter applied this principle to all of the single-acting pumping engines that he made, cutting off the steam by the main steam valve, and at from one-half to two-thirds of the stroke of the piston on the downward stroke, the pressure on each side of the piston being in equilibrium on the upward stroke (Farey 352). But although Watt invented and patented the double- acting rotative steam engine in his second patent, dated Oct. 25, 1781, and although he made many of these engines of many different sizes, and was in fact the only maker of them in the world during the long period that elapsed between their introduction and the expiration of his extended patent in the year 1800, he never used steam expansively on a rotative engine (see Farey, note at the foot of page 487). The engine that Fulton bought from Watt im 1805-6, and which he placed on the Clermont in 1807, was operated by Watt's hand gear, as shown on Plate XIII. of Farey's Treatise. It was very ingenious, but complicated, made almost entirely of steel tempered blue, and was operated by tappets and detents. No modification of Watt's hand gear, to enable it to cut off the steam on a rotative engine was ever made by him or by others. The engines of all the numerous vessels that Fulton built were copies of the one he bought from Watt. When about eleven years of age I frequently saw the steamboats Fire Fly and Lady Richmond, built by Fulton. Their speed was about four a drawing of the valves then in use on them, showing little or no lap; and although he writes very fully on the lead, he makes no mention whatever in his treatise of the lap or of its effect. In the year 1838 the eighteen locomotives of the Camden & Amboy R. R. had one-sixteenth of an inch lap. In the same year the steamer Great Western made her first passage. Her engines had the D slide, with little or no lap, and carrying 2%4 pounds pressure per square inch. She had a separate cut-off valve somewhat like the camboard, but it was never used, the low pressure of steam rendering it almost useless. I have not met with an account in any publication, up to the year 1838, describing increased lap either in text or drawings. The link motion was applied to the slide valve about that date. And in con+ junction with it, in the course of a few years, the lap was gradually in- creased to its present extent, both liberating the exhaust in advance of the admission of steam and forming the efficient expansion gear in use on locomotives and screw steamers. Hoboken, N. J., April 2, 1897. FRANCIS B. STEVENS. : Mr. Fletcher adds the following to the foregoing letter: "Our prac- tice with the Stevens cut-off at the W. & A. Fletcher Co. has included its installation on over two hundred steamers new and old, large and small. We try to find out the amount of work required of the engine, and the necessary steam pressure, and then set the cut-off to suit. With the fixed cut-off, the owner need only notify his engineer of the proper steam pres- sure, and he runs with his throttle wide open. This plan gives a steadier and more regular running of the boat upon its time-table than will be secured from adjustable cut-off in not too competent hands. Not long since the writer was upon a steamer in New York harbor, for which we had made a new cylinder and front in 1855, and had then applied the Adding a 30-foot Section to the Hudson River Steamer New York. (See Marine Review of Dec. 2.) and a half miles an hour. I also frequently saw Watt's hand gear in op- eration; and remember on one occasion seeing the detents fail and the engine instantly stopped. No lead could be given by the hand gear; and the cranks were carried past the centers by a flywheel. All of Fulton's steamboats had flywheels geared two to one, thus increasing the force of momentum fourfold. In the year 1814 Robert L. Stevens built the steam- boat Philadelphia on the Delaware, the engine having Watt's hand gear. And in the year 1817 he invented the camboard cut-off, previously men- tioned, and attached it to this engine as a separate cut-off. This was made by a butterfly valve placed on the steam pipe at its junction with the Bae chest, and operated by two cams on the main shaft, pressing against the camboard and connected to the butterfly valve, and to a strong spring on its arm by a rod about half an inch diameter. -- The lenigth of, the ae corresponded to that of.the cams, and the motion was exceedingly rapid. € at the same time increased the pressure from 2% to 10, pounds per square inch. This cut off was very successful and remained in use on alll OW-pressure steamboats in this country long after the hand gear of Watt ad been superseded by the eccentric of Murdock, and up to the intro duction of the Stevens cut-off in 1840. ; EP Eg ree I also send the following account of the eccentric, deriving its mo oe from the shaft which superseded the plug tree, tappets, and se a Watts, and was applicable alike to poppet and slide valves; and also a an account of the slide valve. These were both patented by William Murdock, the foreman ccc ner of Watt, in 1799. The D slide is shown on plate XVI. opens oe im another form, now generally used, by Fenton, Murray & Co., a f d XVIII. A notable circumstance in regard to the slide ne is t at a to the year 1838, although it was then in universal use on the neue oe and marine engines of England, and also on the lssomore a = country, it had only sufficient lap, or cover, aS It was then Che i he vent the steam from blowing through the cylinder. The ( oan se Pambour, in his famous treatise on the English locomotive in er Stevens gear. It remains in good working order, and has given no trouble. With very fast running engines, the wipers are made slightly dif- ferent in shape, and-we put springs on the lifting rods so as to force the toes to follow down the wipers. But we have never had any trouble to make the cut-off work satisfactorily. I do not wish to be understood as opposing adjustable cut-off gear. We have made and fitted a large num-~ ber of engines with Sickels' dash-pot cut-off with adjustable gear with most excellent results. But there are often advantages in having so simple an arrangement as that which increases the speed by increasing the pres- sure, and which diminishes it, by closing the throttle." A graphic illustration of what forced or induced draft is destined to accomplish is shown in a picture of the works of the B. F. Sturtevant Co., Jamaica Plains, Boston. Two chimneys, one tall stack of 60 feet and the other only a few feet in height, appear in the illustration. The small chimney has taken the place of the tall one in the operation of the works. The results obtained--a steady draft and saving of fuel--seem to indicate that the draft apparatus will some day take the place of tall expensive chimneys, and at the same time solve the smoke nuisance difficulty. The Sturtevant company is probably the largest manufacturer of fans and blowers in the world. All the United States war ships and the principal transatlantic liners, as well as a number of lake vessels, are equipped with these machines, the number ranging from one to thirty or forty. Wide spread operations in this special line of engineering has secured to the ex- perts of this company a vast accumulation of practical information on the subject of artificial draft, which is to be found only in such a concern. A book dealing with the results of the company's experience is to be pub- lished soon. It will contain about 500 pages, the contents of which would warrant sale at $10 a copy to owners or managers of steam plants. The book is being very carefully prepared. Considerable space is given to plans of draft for marine service.