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gineer. Fig. 10 represents the shifting link fore and back gear, and for forward and back motion, in mid-gear, at beginning of the back strokes, may be had. This the shifting link stroke. The origin of the link motion, in an fails to give; the lead hero varies with the eximpracticable form however, has been traced pansion, being least in full gear, and a maxito a Mr. Williams of Newcastle; it was worked mum in mid-gear; but it may be made the out by Mr. Howe, and applied to Stephenson's same for the forward and back strokes. An locomotives, and is generally accredited to admission through .75 = 4 stroke, is attended Robert Stephenson. The motion attained is with a mean expansion of 16 per cent., with equivalent to that of a variable eccentric. If release at .91 of stroke; while .50 admission two eccentrics be differently set on the same gives about .30 expansion, exhausting at .80=; axle, each will be the equivalent of a crank, stroke. The least attainable percentage of adgiving to its rod a definite throw or stroke mission, with the different forms of link, varies equal to twice the eccentric radius; and the from 11 to.17 of stroke.—If, in an engine workmovement of either eccentric in any part of its ing under a given set of conditions, including & revolution can be resolved into two component given action of valve gear, the boiler cease to motions, tangential and radial. Now, in the supply the number of cylinderfuls of steam relink motion, two eccentrics have their centres quired at the velocity, the pressure on the pisof form in nearly opposite directions from the ton and the speed proportionally fall; or if the same axle on which they turn, and their rods, ascent of grade increase, the resistance and instead of attaching to the valve rod, take hold work being greater, the piston cannot advance of the upper and lower ends of a curved, slot- 80 rapidly, and the speed again falls, unless the ted link; the valve rod by a stud or a pin within power of the boiler suffice to raise the tension the slot can be so shifted as to be worked from of the steam. On the other hand, if while the either end of the link, or from intermediate grade remains the same the steam pressure points in its length. The motion of the link rises, or the pressure the same the grade diis compounded of the distinct motions of the minishes, the engine runs faster, and until the eccentrics, which, as respectively intended to increasing resistance mounts to an equilibrium give forward and backward strokes, are called with the power. Thus the true measure and the fore and back eccentrics. The motion of limit of power of the locomotive engine are in each eccentric prevails in that half of the link the evaporative power of the boiler. But the to which it is coupled, the motion at middle calculations of power and speed belong to the point being equally composed of the two; so subject and works of railway practice. The that the horizontal movement, distance of following table presents some examples of the travel, or throw which the link will impart to tractive resistance per ton gross of engine, tenthe valve rod, is a minimum when the rod is der, and train on a level: actuated from the middle of the link, and increases toward the extremities, but with a movement in the two in opposite directions. The link is shifted, or the block and valve rod pin within it, by means of the reversing lever at the hand of the engineer; and thus various lengths and speeds of throw of the same valve are secured with various periods of admission, expansion, and release of steam.

Link motions are thus of two classes: 1, the stationary -Since about the year 1830, and until within link with shifting block; 2, the shifting link a few years past, the rapid improvement and with stationary block. With these the results introduction of railway locomotion had quito attained slightly differ; and beside, the prin- absorbed the attention of inventors, and the ciple, application, and effects of the link mo- problem of steam carriage on common roads tion are capable of very great variation. Usual was comparatively neglected. The difficulties dimensions are, to give to the valve a lap of 1 in the way of such propulsion of vehicles, moreinch, lead, inch; the throw of each eccentric, over, remain considerable. In the great exhi4inches; length of eccentric rod, 54 inches; bition of 1851 there was but one locomotive length of the link between attachments of these for common roads exhibited; but since that rods, 12 inches; with dimensions of the sub- time, in England, no fewer than 9 varieties of sidiary links and levers in the proportions re- such engines have attracted attention, some quired. Then, certain main positions of the of which have been employed for agricultural link and valve rod, as secured by the reversing or for carrying purposes, and perhaps the most lever, are as follows:

successful of which are the traction engines of Bray and Boydell, Among those interested in the subject in the United States, Mr.

J. K. Fisher has thus far been the most sucHalf gear forward.

cessful. He built in New York in 1852 a small Mid-gear...

experimental steam carriage, with easy springs.

This, on the Broadway pavement, in night With the stationary link a constant lead, through trials, outran horses; but it had not steam

Resistance, lo lbs. per ton.

Speed,
in miles per hour.

Under superior

conditions.

Under ordinary

conditions.

10
20
80
40
60
60
70

8.6 10.3 18.2 17.3 22.6 29.0 86.6

18,0 15.5 20.0 26.0 84.0 43.5 65.0

Positions.

Eccentric

used.

Length of trav!
of valve, inches.

Full gear forward.

Fore.
Fore.
Both.
Back.

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Full sear backward.

enough for common roads. He has now (1862) the season, at an average of 71 miles an hour, nearly completed a large carriage; and four did not still lead to the general introducself-propelling fire engines of Messrs. Lee and tion of steam propulsion; though this clearLarned's patent (see FIRE ENGINE) have been sighted pioneer predicted the navigation by built, so far as their locomotive apparatus is such means not only of the western waters of concerned, on his plan. These all have springs America, but also of the Atlantic ocean. Thus, of great flexibility, and yet run as steadily as the actual moving of boats by steam certainly ordinary carriages. This result is attained by occurred in this country, and perhaps in France, using radius rods to hold the driving axle at a before the trials of Miller and others in Scotconstant distance from the engine shaft, which land, on which latter, however, the English revolves in fixed bearings in the main frame, endeavor to found their claim to priority. Patallowing the axle to swing or to rise and fall, rick Miller and William Symington, in 1788, parallel rods being introduced to transmit the propelled on Dalswinton loch twin or double power. The parallel and radius rods termi- pleasure boats, by means of a paddle wheel nate in ball and socket joints; and the lateral placed between them, and by an engine with swing is limited by a transverse radius rod held à 4-inch cylinder, attaining 5 miles an hour. by a spring. By these several methods, not With a larger engine, in 1789, they navigated only are the necessary lateral movement and the Forth and Clyde canal, at a rate of 6 to 7 flexure due to roughness of roads allowed, but miles an hour; but owing to insufficiency in also the rolling or oscillation of the carriage, the machinery, they were compelled to abanwithont twist of the frame, or interfering don further attempts. In 1796 John Fitch with the accurate transmission of the power to moved a small boat on the Collect pond, in the driving wheels. Of the steam fire engines, the city of New York, by a small engine and a the cylinders are of 7 inches diameter and 14 worm or propellor screw projecting from the inches stroke; the valves operated by a station- stern of the boat; this being, probably, the ary link with reversing lever, and securing ex- first employment of the screw for propulsion. pansion in any desired degree. The power is In the same year a work was published in derived from Lee and Larned's annular steam Florence, claiming that an Italian, Serapino boiler. The speed of steam carriages on good Serrati, had successfully propelled a boat by common roads has been made to reach 30 miles steam on the Arno; if this be true, still no per hour for short distances, and for journeys further practical result followed upon it in of three miles 20 miles per hour.-Steam Nav- that quarter. Meanwhile, Robert Fulton was IGATIOX. Paddle wheels, propelled by wind- in England and in France, and, if not previouslasses turned by men, or by animal power, were ly interested in steam propulsion, became so to some extent in use in the war galleys of the upon inspection of Dr. Cartwright's steam ancient Egyptians and Romans; it is uncertain barge, and Earl Stanhope's boat with duckwhether they afforded any essential advantage feet paddles under the quarters, neither of orer the use of oars. Even if Blasco de Garay, which however proved successful. In 1798 mentioned in treating of the steam engine, ac- the legislature of New York granted to Chancomplished what has been claimed, the entire cellor R. R. Livingston of that state, who had abandonment of his project shows that it must been experimenting with steam for boats, the have been unsatisfactory; so that he can in no right to navigate the waters of the state by way be regarded as the originator of steam steam for 20 years; and though he failed to navigation. The attempts made in England and satisfy the condition of the grant by propelFrance, prior to 1730, led to no result. Jona- ling a boat 4 miles per hour within the year, than Hulls in 1736 described a method of pro- the grant was in 1803 renewed, and the time pulsion by a stern wheel acted upon by an atmos- of fulfilment extended to 1805, and afterward pheric engine; but he is not known to have put to 1807. In 1801 Mr. Symington completed for his plan in practice. In France, from 1774 to Lord Dundas & steamboat, the Charlotte Dun1796, the count d'Auxiron, the brothers Périer, das, its engine having a horizontal cylinder of the marquis de Jouffroy, and M. des Blancs 22 inches diameter and 4 feet stroke; this made, severally constructed and tried boats to be pro- with boats to 140 tons burden in tow, on the pelled by steam, none of which were success. Forth and Clyde canal, 37 miles per hour; but fal. In 1786 John Fitch, of Pennsylvania, pro- a prejudice excited by its washing the banks of pelled by a very small engine, cylinder one the canal compelled its abandonment. About inch in diameter, a skiff ‘at fair speed; and in 1799, Mr. Livingston meeting with Fulton in the same year, by a 12-inch cylinder, a boat on Paris, they became together interested in prothe Delaware, the speed however being in this jects for steam propulsion, and, notwithstandcaze very slow. In 1787 Rumsey, of Virginia, ing the jealousy of Des Blancs, made at least attained a speed of at least 3 miles an hour on two experiments on the Seine previous to 1804, the Potomac, by reaction of water taken in at neither of which succeeded. The breaking in the bow of his boat by & steam engine and the middle and sinking of their boat in the first forced out at the stern; he tried this plan in instance by the weight of the engine, is beEngland in 1793, making 4 miles an hour. lieved to have led to Fulton's subsequent inFitch's boat of larger size, placed on the Dela- troduction of the strong and light framing inFare in 1790, and making regular trips through tended to uphold the weight of large engines,

VOL. XV, 5

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which is one of the characteristic excellences ocean steam navigation. (See STEVENS.) He of American steamboats. It was in 1804 that also greatly improved the speed of his boats, Oliver Evans, at Philadelphia, propelled his attaining in 1814 to 134 miles an hour. In steam dredging machine, the Oructor Amphib- 1812 th first regular passenger steamer in olis, upon wheels on land, and subsequently Britain, the Comet

, built for Henry Bell, apby a paddle wheel upon the water. In the peared on the waters of the Clyde. This vessame year John Stevens, of Hoboken, N. J., sel was of 40 ft. keel, 101 ft. beam, 25 tons propelled in the waters about New York á burden, and 3 horse power; her speed was 5 small boat by means of an engine, the steam miles an hour. In 1814 Boulton and Watt first for which was furnished by a very small tubu- applied two condensing engines, connected lar boiler, the power being applied by means with the shaft by cranks placed on it at right of a form of screw also invented by him, and angles, in a steamer to run upon the Clyde. This substantially that most approved at the present plan has since become for boats of larger size a day. Fulton, meanwhile, had again visited very general one. In 1818 the Savannah, a England and Scotland, inspecting in the latter New York built ship, with side wheels, and country one of Symington's later boats, and propelled by steam and sails, crossed the Atreceiving from him information respecting its lantic to St. Petersburg via Liverpool, reaching construction and working. Returning to New the latter place direct from New York in 26 York in 1806, he commenced at once building, days, and returning in safety. Although this in conjunction with Mr. Livingston, a steam- was the first crossing of the Atlantic by steam, boat for use upon the Hudson. This boat, the yet as the ship had but small engines, and was Clermont, was of 160 tons burden, 130 ft. long, 18 unsuited to the risks of such à voyage, the ft. wide, and 7 ft. deep. She was provided with event scarcely demonstrated the practicability an engine from the establishment of Boulton and of ocean steam navigation. The first regular Watt, with a single cylinder 2 ft. in diameter passages were made by the Sirius and Great and of 4 ft. stroke;

boiler 20 ft. long, 7 ft. deep, Western in 1838, the former making the trip and 8 ft. broad. The diameter of the paddle from London to New York in 17 days, and wheels was 15 ft., the boards 4 ft. long, and the latter from Bristol to New York in 15 dipping 2 ft. in the water. On the morning days. In 1811 Fulton and Livingston estabof Aug. 7, 1807, Fulton with a few friends and lished a ship yard at Pittsburg, and built an mechanics, and 6 passengers, and leaving on experimental boat, the Orleans, the first ever the shore an incredulous and jeering crowd, placed on our western waters. This boat had started for Albany. The distance, 150 miles, stern wheel and masts; her first trip from he made at a speed of nearly, and on his return Pittsburg to New Orleans was made in the of full, 5 miles an hour. As the speed was still winter of 1812. This seems to have been the less than had been anticipated, the boat was first successful application of the stern wheel, lengthened to 140 ft. keel, and, being other now in very general use on the western rivwise altered, was early in the year 1808 placed ers, especially for boats of light draught. for regular trips on the Hudson between the (See also Sup.) Of the best class of American cities already named. By tracing thus far the river steamers, a good example is the New history of steam propulsion on water, we find World, built in 1847, of 1,400 tons, and placed that Fulton cannot be said to have been the on the Hudson between New York and Albany. originator of steam navigation, nor indeed the Her engines were built by the firm of T. F. inventor of mechanism for such navigation; Secor and co., condensing, of 76 inches diameter but the credit belonging to Fulton is that of and 15 ft. stroke, provided with double balance having been the first successfully to cross the valves and Stevens's cut-off, worked by the chasm from mere attempts to positive achieve- usual eccentrics, lifter rods, and rock shafts ment—the man through whose energy and skill with their levers; the two boilers being circuwas first secured that combination of means lar, and with single return flues. Of this boat which rendered navigation by steam at once the length is 375 ft.; breadth, 36 ft., over practicable and profitable. Very properly, guards 69 ft.; depth of hold, 10 ft. 6 in.; the therefore, do the committee of the first London average speed of run, landings not included, is exhibition, 1851, say: "Many persons, in va- 18} miles per hour. The steamers City of Bosrious countries, claim the honor of having first ton and City of New York, running on Long invented small boats propelled by steam; but Island sound, embody a more recent style, in it is to the undaunted perseverance and exer- some respects, of construction and of propelling tions of the American Fulton that is due the machinery; their engines are from the Novelty everlasting honor of having produced this rev- iron works, New York, hull by Sneeden and co. olution, both in naval architecture and naviga- The Daniel Drew, running upon the Hudson, tion." Within a brief period after the first trip has recently made, on a trial trip, a speed of of the Clermont, Mr. Stevens launched his 22 miles per hour. The successful introduction boat, the Phænix; but as Fulton's success had of the screw was through the experiments of secured the right to navigation of the waters Capt. Ericsson and F. P. Smith, on the Thames, of New York, R. L. Stevens, son of the former, in 1837. The speed attained, with a large ship boldly took this boat round to Philadelphia by in tow, and against tide, was 41 knots an hour. sea, this being indisputably the first instance of The next screw vessel, the Robert Stockton,

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built in 1839 for an American gentleman, was advance of a screw against the water, which also successful; while the success of the Archi- corresponds with a given rate of turn called medes, in 1840, of 232 tons and 80 horse power, the “ pitch," the number of revolutions of the Fas so great as to attract the attention of the screw must be increased; and as the pitch best English admiralty; and from this time the for effect is limited by the diameter of the screw advanced rapidly into favor, employed screw, and this by the draught, and as for each either as sole or as auxiliary means of propul- revolution of the screw two journeys of the sion for men-of-war or fast-sailing merchant piston are allowed, the time, and hence the vessels.—Many peculiarities in the construction stroke, is necessarily short; the disadvantages of marine engines, their accessories, working, are, the more frequent recurrence of the dead and forms of boilers, have already been men- points, a proportionately greater loss of steam tioned in treating of the steam engine. To in filling the passages to the cylinder, and a combine the three things requisite in a steam narrower limit to the employment of expansive Fessel, the ship, the engines and boilers, and working. Still in most marine engines, wheththe wheels or other propeller, each of which is er for paddles or screws, steam is worked exin itself a complex study, is one of the most pansively, though seldom to the same extent as difficult problems of modern engineering, de- in land engines; the best results being secured manding in the highest degree theoretical at- when the cylinder is surrounded both with tainments and practical skill. The marine jacket and clothing, or the steam sufficiently steam engine is necessarily made as light, com- superheated. In respect to the necessity of pact, and at the same time as economical of preventing accumulation of saline matters in fuel as possible. One of its oldest varieties, the the boilers of sea-going vessels, with consequent side lever form, is still in use in some of the raising of the boiling point and tendency to largest paddle steamers, among them those of scale within the boilers, it is now the usual the Cunard line. Although it has many ad- practice to blow off the requisite quantity of Fantages, yet, in view of the value of space and brine continuously, and from the surface as weight in merchant and passenger steamers, it well as the bottom of the boiler, in due prois probable that the lighter and more compact portion to the quantity of feed water admitted, direct-acting forms of engine, though more ex- so as to keep the water at that degree of satupensive in working, are in the total more eco- ration found by experience to be attended with Domical. The screw propeller, or screw, which little or no deposit. The density of the brine is the means of propulsion in those vessels is known either by the hydrometer, or by innamed from this circumstance screw steamers struments for the purpose termed salinometers. or propellers, consists in its simplest form of a One of the most dangerous and troublesome Fery strong metallic plate, standing edgewise tendencies of a boiler is that known as primon à cylinder or shaft, and winding round it ing, as, beside the great loss of heat and of like the blade of an auger, or of two or more steam pressure occasioned by it, it may also blades or vanes, forming parts of such spirals. cause the breaking down of the engine by the The shaft is made very strong, continued with- shock of the piston on the incompressible fluid in the hold of the ship, and intended to revolve. in the cylinder. Remedies resorted to are, the The screw or blades are upon that part of it increase of size of the steam chest, increased projecting from the stern of the ship, and space height of the steam pipe orifice above the surfor the turning of the blades is allowed by a ver- face of the water, and sometimes the adding tical oblong recess in the keel and stern, just of tallow to the water in the boiler. By before the rudder. The position of the shaft is the throttle-valve of marine engines, the flow such that the screw shall usually be wholly of steam to the engines is usually regulated stabmerged; and upon the portion of the shaft or shut off by hand. The ordinary vertical within the hold one or more engines are made form of governor is of course wholly inapplito act, either by cranks formed on the shaft, cable, through the pitching and rolling to which or by means of geared wheels. The use of such the ship is liable. But in a heavy sea, one wheel wheels admits of a slow speed of piston with a or the screw being sometimes lifted quite out high speed of the screw; while on the other of the water, the engine begins to “race," i. e., hand these wheels are necessarily cumbrous, to fly off at very high velocity, the liability to their wooden teeth are liable to be “stripped” or this result being greater with screw than with broken off by a sudden stroke of the sea upon paddle steamers; and in such case an automatic the screw, and they are unavoidably attended and prompt-acting substitute for the hand bewith a loud and disagreeable rumbling noise. comes very desirable. The desideratum in these Vessels of considerable draught admit of a diam- cases has recently been supplied by 3 or 4 difeter and pitch of screw sufficient for propulsion, ferent contrivances. The earliest of these were without undue speed of the piston and without Silver's “momentum-wheel governor," and his gearing. In the best marine engines the de- "four-ball” or “balanced governor ;' these indoetion for friction, the working of valves, struments act equally well in any position. The pumps, &c., from the indicated or gross horse same result is secured in a more recent invenpower, in order to find the effective or avail- tion, Porter's “marine governor," with susable propulsive power, may be taken as usu- pended and balanced balls, acting by compresally about 25 per cent. To increase the linear sion, according to speed, of a spiral spring. In

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all these forms it is true that the remedy must current after it, the screw acting in this current be applied after the evil has begun to develop causes the vessel to advance faster than the itself. Jensen, of Copenhagen, has accordingly blades of the screw at the same moment are attempted to produce a prompt and perfect entering the water or would enter a solid marine governor, by admitting the water of surrounding them. Owing to the current, the sea to rise in two small cylinders directly however, the real slip is not apparent. In refthrough the bottom of the vessel, and as near erence to the comparative value for propulsion as may be to the screw or wheels; pistons of paddle wheels and screws, it may be said that moving on and with the water in these cylin- when both are in their best trim, and well proders, are made by levers to control the steam portioned to the vessels and the engines, they, valves; and thus the irregular immersion of are about equally efficient. The screw, howthe vessel itself is caused to regulate the supply ever, in ordinary weather, is apt to have a more of steam to the engines.—Paddle wheels are uniform immersion and action; while a great generally of two kinds, those with common or disadvantage of its use is the increased speed fixed, and those with feathering floats. Wheels which must be given to the engines. with fixed floats, when a vessel is anchored or STEARIO ADID (Gr. oteap, tallow), a fatty is yet moving slowly, act at great disadvan- acid obtained from mutton suet, and other fats tage; since those entering the water strike it that contain stearine, by the process described obliquely, and waste much of the power in & in CANDLE, vol. iv. p. 355; symbol, HO,Cs. tendency to lift the bow of the vessel, instead H3.03. When recrystallized from ether, unof propelling it, and those leaving the water til the fusing point becomes constant at 159°, lift much dead weight in the form of back wa- and slowly cooled, the acid forms beautiful, ter. But when the vessel has acquired fair or colorless, transparent, rhombic plates; these rapid speed, its very motion largely overcomes melt into a colorless oil, tasteless and without these difficulties, and the dip of each float into odor, and when quickly cooled the substance the water, and its withdrawal out of it, virtu- concretes in a white crystalline mass, which is ally occur nearly edgewise, the effect being insoluble in water, but readily forms with hot similar to the “ feathering” of an oar by the alcohol a solution having acid reaction. It is rower. But with a paddle wheel badly pro- the material of the so called stearine candles. portioned, immersed too deeply in the water, Stearic acid exists in fats in combination with or attached to a slow boat, the unfavorable glycerine, forming stearine, from which it is action above referred to is largely experienced. separated by saponification. (See GLYCERINE.) By making the floats movable about horizontal It combines with numerous bases, and forms axes through the middle, and controlling their with them both acid and neutral salts, called position by a second wheel, set eccentrically stearates. Stearate of soda is the basis of orto the paddle wheel, as well as in other ways, dinary hard soap; stearate of lead is one of the they are made to feather on entering and leav- constituents of the common lead plaster. ing the water. By such arrangement the speed STEARNS, a central co. of Minnesota, boundhas been increased, and the vibration due to ed E. by the Mississippi, and drained by Sauk the movement of the wheels greatly reduced. river and lake; area, 1,379 sq. m.; pop. in The excess of the velocity of the wheel above 1860, 4,505. A portion of the county is prairie, that of the vessel, called the slip, is in favora- but the W. part is mountainous. There are nuble circumstances about į the speed of the lat- merous lakes and streams. Capital, St. Cloud. ter; feathering wheels have less slip. As, STEATITE, or SOAPSTONE, a compact variein the screw, one, two, or three threads are ty of the mineral species talc, consisting of silireadily placed within the distance of a single ca 62.14, magnesia 32.92, and water 4.94 per coil, we have thus single-threaded screws, cent., being a hydrous silicate of magnesia. It double-threaded, and so on. The distance to occurs in massive beds among the metamorphic which the screw would enter a solid during a rocks, often associated with serpentine. The single revolution, is of course the distance or stone is distinguished by its soft and uniform length of one complete turn; and this is the texture, which admits of its being cut by the measure already named the pitch of the screw. knife or saw, especially when freshly quarried, But since, worked in water, the medium gives and also by its property of withstanding inway in part before it, the screw does not ad- tense heat. Its colors are coarse gray and vance the full amount of its pitch, and this de- grayish green, sometimes yellowish; the texficiency is called the slip of the screw. Sup- ture generally granular; lustre dull; specific posing the screw cut into portions by planes at gravity 2.65 to 2.8; structure compact, someright angles to its axis, these would be the times lamellar; and to the touch it is greasy vanes or blades; and according as the screw like soap. When crystalline or in thin and was two-threaded or three-threaded, two or flexible folia of pearly lustre, it is commonly three of these would stand opposite each other. known as talc, of which the substance employThis form, in which each blade is but a small ed under the name of French chalk for removportion of the complete pitch, is that now com- ing grease spots is a variety. Meerschaum is monly in use. What is called negative slip in another variety. The uses of soapstone are propeller screws, is that result in which, ow- numerous, and beds of it furnishing large ing to the drawing by the ship of a wake or blocks unmixed with other substances are val

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