1,967 tons, equal to 4,406,080 pounds, which gives 2.14 pounds of coal consumed in the mill, for all purposes, for each indicated horsepower exerted one hour.

It may be thought that too much space has been given to this test; but it is so good an example of valuable work within the reach of nearly all users of steam-engines, that it has been thought well to bring it to notice in this manner.

The Putnam Machine Company, Fitchburg, Mass., were among the earlier manufacturers of an excellent class of automatic cut-off, horizontal engines, of medium speed and moderate power.

Being well described in Tolhausen's Uhland, it will be unnecessary to describe them here. By the use of double-seated poppetvalves and an ingenious combination of cams and levers, the cut-off is controlled by the governor, and an excellent distribution of steam is effected, with satisfactory uniformity of speed.

The writer has occasionally tested an engine of this construction, 12-inch cylinder, 30-inch stroke, during a period of 17 years, and always found it tight, and in perfect order, almost without repairs. This valve-gear is not well adapted to speeds higher than 90 or 100 revolutions per minute.

Charles H. Brown & Co., also of Fitchburg, by means of gridiron. slide valves, actuated by cams and levers, and detaching mechanism controlled by the governor, obtain very prompt and full admission, almost instantaneous cut-off, and free release, and produce indicator diagrams almost ideally perfect.

In point of mechanical execution and finish, the Brown engines are singularly beautiful, and in all the higher qualities of design and proportion they are excellent. This engine, also, is described in Tolhausen's Uhland.

The Fitchburg Steam-engine Company, also of Fitchburg, Mass., a newer enterprise, is now making an automatic cut-off engine of much higher order than the small vertical engines described in Tolhausen's Uhland.

They make a peculiar form of centrifugal governor placed on the crank-shaft; a kind of governor which has gained great favor within the last ten years, and assumed a multitude of forms. We shall again have occasion to speak of this governor.

In the form under notice, which is excellent, the eccentric is guided in its transverse motion across the shaft, by means of a sort

of parallel motion, consisting of two levers connected with ears on opposite sides of the eccentric-block, describing equal arcs in opposite directions; thus avoiding the guides used in some other forms, while preserving constant lead of valve. Weights attached to these levers exactly counterbalance the weight of the eccentric and its strap, and, in vertical engines, the weight of the valve-rod and connections also, in all positions, leaving the eccentric neutral under all the impulses of the governing mechanism. This consists of weights. on arms pivoted to opposite sides of an incasing pulley, connected by rods to the balancing-arms already mentioned, acting centrifugally with a force proportioned to the rapidity of revolution, opposed by springs which act centripetally with a force proportioned to the compression produced by the revolving-weights.

These forces being properly adjusted, so as to be in equilibrium at normal speed, this speed will be maintained so long as the load and the mean effective pressure of steam in the cylinder remain relatively unaltered.

Any increase of load, with steam-pressure constant, will cause a corresponding diminution of velocity, and therefore of centrifugal force in the weights, and give a preponderance to the springs acting centripetally, so as to turn the eccentric to delay the cut-off, and so to increase the mean effective pressure. On the other hand, any diminution of load will give preponderance to the centrifugal force of the weights, and turn the eccentric so as to hasten the cut-off, reduce the mean effective pressure.

and

When a single piston-valve is used, release and exhaust-closure are affected in the same sense as cut-off: with early cut-off, there is early release and early closure of the exhaust; and with later cut-off, both release and closure are retarded, as in a link-motion.

The single valve is used only in the smaller engines, especially in vertical engines. In larger, horizontal engines, from 9-inch diameter and 24-inch stroke to 24-inch diameter and 48-inch stroke, two piston-valves are used, both in one divided steam-chest at the side of the cylinder: the upper valve, double-ported, controlled by the gov ernor, producing admission and cut-off; the lower, single-ported, moved by an ordinary eccentric, controlling release and compression.

Only moderate speeds are calculated on, -75 revolutions per minute for 48-inch stroke, and 125 revolutions for 24-inch stroke, corresponding to 600 feet per minute piston-speed in the former case, and 500 feet in the latter. No scientific tests of these engines have been made; but diagrams taken from them are excellent, and they bear a good reputation.

William A. Harris, Providence, R.I., has long manufactured a class of steam-engines, which, under the name of Harris-Corliss engines, frankly recognize their indebtedness to Mr. George H. Corliss, but with sufficient modification of detail to justify the qualifying prefix of Mr. Harris's name.

A particular description of the modifications introduced by Mr. Harris, such as his self-packing valve-stems, his peculiar form of releasing tappets, and his rather larger pins and connections in the valve-gear, hardly falls within the scope of this paper, and will be found in Tolhausen's Uhland. These engines are largely used. Indeed, Mr. Harris enjoys the honorable distinction of having been one of the very few who recognized the merits of the Corliss engine and the rights of Mr. Corliss, and took a license from him to build his engine before the expiration of his patents. An account of a competitive test of one of these engines is given below.

The Reynolds-Corliss Engine, built by E. P. Allis & Co., Milwaukee, is in nearly all essential respects a Corliss engine, — with certain modifications of detail, more or less important, - which has obtained a wide reputation, and made an excellent record. It is described in Tolhausen's Uhland, and its peculiarities cannot be dwelt on here. An account of a trial of one of these engines, in competition with one of each of the preceding and following engines, will be found below.

Jerome Wheelock, Worcester, Mass., makes an engine which is, in all its most important features, a Corliss engine, yet more extensively modified. The valves, no longer cylindrical segments, as in the Corliss, the Harris-Corliss, and Reynolds-Corliss engines, are segments of conic frustums, provided with steel collars, serving as "steps," to adjust them endwise in their seats.

All four of the valves are placed below the cylinder, which is horizontal, the cut-off valves being placed directly back of the steamdistributing valve, so that the cylinder has but two ports, corresponding in position to the exhaust-ports of the Corliss engine. Exhaust takes place through a "cup" in the steam-distribution valve.

This engine is also described in Tolhausen's Uhland. Three engines of the three last preceding styles Harris-Corliss, Reynolds-Corliss, and Wheelock were elaborately tested by Mr. John W. Hill at the Millers' International Exhibition, Cincinnati, O., in June, 1880.

A table of the leading dimensions of these three engines is subjoined.

CONDENSED SUMMARY OF RESULTS-CONDENSING (Concluded).

The air-pump of the Harris-Corliss engine was driven by the engine; that of the Reynolds-Corliss, by a separate engine or steam-pump. The Wheelock engine had a Buckley siphon condenser, requiring only sufficient power to lift the water to supply it.