tion is as seen in the sketch.' A is the steam-pipe, B the starting-valve connection, C the receiver, D the exhaustpipe, and v and Vare the starting and the intercepting valves. The engine here taken for illustration is an English passenger locomotive, having 16- and 20-inch cylinders, 24 inches stroke, drivers 801 inches in diameter. The steampressure the same as the preceding, and the weight of engine 97,000 pounds, of which 68,000 rests on the driving-wheels. The areas of heating and grate surface are, respectively, 1,323 and 17 square feet. Joy's valve-gear is employed.

The construction of the valves is seen in the next figure. The flap-valve is the intercepting valve, seen as in regular working. Its spindle is connected with the small piston at a, as shown. The starting-valve is set in a pipe or casing connected with the former, as seen in the sketch. A valve held in place by a spring connects the pipe b with the piston a. The starting-valve is worked by the enginedriver, the same motion closing the intercepting valve, and the locomotive starts as a simple engine. The rise of pressure in the receiver presently restores the valves to the position shown, and the engine at once becomes compound.

Steam-pressures have risen, since the improvement of the steam-engine by Watt was begun, somewhat as follows, at sea and in condensing engines:

In many cases considerable variations from these figures have been observed, but they may be taken as representative.

The following have been considered fair average figures as representing what was good and standard practice at the dates given, and as illustrating the progress effected in marine engineering in the period 1870-1900:

The Clermont, the first successful steam-vessel of Robert Fulton, has now for its lineal descendants vessels like, for example, the steamer New York, built eighty years later, for the same route, by the Harlan & Hollingsworth Company, and "engined" by the W. & A. Fletcher Company (Fig. 152). The dimensions of hull are as follows:

The wheels are aft of the centre of length, instead of forward-a great improvement in the appearance of the boat.

The engine is a beam-engine, with a cylinder 75 inches diameter and 12-feet stroke of piston, provided with Stevens's cut-off. The use of a surface-condenser instead of a jetcondenser in this river-steamer is a change made to overcome the evil of using mixed salt and fresh water in the

boilers, as the tides extend to Albany and the water changes from salt to fresh en route.

Another change is the return to the use of Stevens's feathering wheels. These are 30 feet 2 inches diameter

outside of buckets. There are 12 curved steel buckets to each wheel. Each bucket is 3 feet 9 inches wide and 12 feet 6 inches long. The wheels are overhung, and they have a bearing on the hull only. The feathering is effected in the usual manner by driving and radius bars, operated by a centre placed eccentric to the shaft and held by the "A-frame" on the guard. These wheels were introduced in the New York for the purpose of gaining speed, and the trial-trip shows that the builders' expectations were completely fulfilled. Absence of jar is another gain obtained by the use of these wheels, and the comparatively thin buckets enter the water so cleanly and smoothly that one notices none of the shake so common on boats with the ordinary wheels.

Steam is supplied to the engine by three return-flue boilers, each 9 feet diameter of shell, 11 feet width of front, and 33 feet long, constructed for a working pressure

of 50 pounds per square inch. Each boiler has a gratesurface of 76 square feet or 228 square feet in all, and with the forced draught produce 3,850 horse-power.

The exterior is of pine, painted white, relieved with tints and gold. The interior is finished in cabinet-work, and is all hard wood, ash being used forward of the shaft on the main deck, and mahogany aft and in the dining-cabin. Ash is also used in the "grand saloons on the promenade deck. The saloon-sides are almost entirely of glass, and the windows so low that persons seated inside have an opportunity to view the scenery.

The Puritan (Fig. 154) illustrates the adaptation of this type of steamer, so nearly perfected by Robert L. Stevens, to that kind of navigation intermediate between river or still-water and oceanic, which permits the retention of some features of the former, while modifying the shape of hull and type of engine to meet the demands of "outside" navigation.

The plans of this steamer are by Mr. Pierce, the details. of hull-construction by Mr. Faron, and the machinery by the W. & A. Fletcher Company. The principal dimensions are as follows: Length over all, 420 feet; length on the water-line, 404 feet; width of hull, 52 feet; extreme breadth over guards, 91 feet; depth of hull amidships, 21 feet 6 inches; height of dome from base-line, 63 feet; whole depth, from base-line to top of house over the engine, 70 feet. Her total displacement, ready for a trip, is 4,150 tons, and her gross tonnage 4,650 tons.

The ship is fire-proof and unsinkable, having a double hull divided into 59 water-tight compartments, 52 between the hulls and 7 made by athwartship bulkheads. In the fastenings of hull and compartments there were used 700,000 rivets and upward of 30 miles of steel angle-bar. decks are of steel, wood-covered. Her masts are of steel, and hollow, to serve as ventilators, and are 22 inches in diameter. Her paddle-wheels are encased in steel.

Her