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him, and by the payment of a considerable Killingworth to drag coal. About this period sum to procure a substitute in the militia, for he invented a miner's safety lamp to obviate which he had been drawn. At this time he the frequent explosions from fire damp, one of was desirous of emigrating to the United States; which had occurred in 1814 in the colliery under but being unable to raise sufficient money to his care. The subject was at the same time pay for his passage and outfit, he set himself brought under the notice of Sir Humphry Davy, steadily to work to repair his losses. In his and both he and Stephenson, though living leisure hours he studied mechanics and engi- hundreds of miles apart, and personally unneering, mended clocks and shoes, cut out clothes known to each other, constructed lamps foundfor the miners, and turned his hand to so many ed upon identical principles, but arrived at inuseful purposes that he was regarded by his dependently by different trains of thought, the fellow laborers in the colliery as a sort of uni- former working out his ideas scientifically, the versal genius. What was of more benefit to latter mechanically. Stephenson's lamp was him was the favorable impression which his practically tested by himself at Killingworth suggestions for improvements in machinery in Oct. 1815, nearly 3 weeks before Sir Humphry made upon his employers, who in 1812 ap- made public his invention, and is still employed pointed him engine-wright at Killingworth, at there. To Davy nevertheless was ascribed the à salary of £100 a year. With this event his priority of invention, and a sum of £2,000 was mechanical genius seemed to take a fresh start, raised at a meeting of coal miners and presentand beside erecting a winding engire for draw- ed to him, £100 being at the same time assigned ing up coal and a pumping engine, he projected to Stephenson. The friends of the latter, deemand laid down a self-acting incline along the ing that injustice had been done him, soon after declivity of the Willington ballast quay, so presented him with £1,000, a proceeding warmarranged that full wagons descending to the ly criticized by Sir Humphry, and which provessels drew up the empty ones.

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voked a bitter controversy between the partistruction of an efficient and economical loco- sans of the rival claimants. Having brought motive steam engine, however, occupied his at the locomotive to a considerable degree of tention beyond any other subject; and after a perfection, Stephenson next turned his attencareful examination of all the machines within tion to the improvement of railways, his opinion his reach, he commenced, and in July, 1814, being that both were parts of one mechanism, completed an engine, which worked success- and that the employment of steam carriages fully on the Killingworth railway, and proved on common roads was impracticable. For the the best yet constructed, though its operation purpose of making his railways solid and level, was by no means satisfactory to the inventor. and to prevent jerks at the junction of the rails, It was the first locomotive made with smooth he took out in 1816 a patent for an improved wheels, and from the outset he rejected the rail and chair, recommended the employment clumsy contrivances which Trevethick, Blen-' of heavier rails and the substitution of wrought kinsop, and others had thought necessary to for cast iron, and established the gauge still secure sufficient adhesion between the wheels generally in use. In connection with these and the smooth iron surface of the rails to al- improvements he added considerably to the low the propulsion of a train. At this early lightness and strength of the locomotive, and day also he told his friends “there was no substituted steel springs for the small cylinders limit to the speed of such an engine, if the on which the boiler had at first rested. Soon works could be made to stand it;" an opinion after the general peace of 1815 the necessities he was subsequently obliged to maintain al- of internal commerce began to suggest the esmost single-handed against the most experi- tablishment of railways, although the employenced engineers of England. While engaged ment of steam power, except for the purpose in plans for an improved engine, his attention of expediting the ascent of heavy grades, was was attracted to the increase in the draught of generally considered impracticable. Stephenthe furnace obtained by turning the waste son and a few others, however, ventured to steam up the chimney-a practice originating believe that the locomotive was destined to solely in the desire to lessen the noise caused supersede the mail coach, and the railroad to by the escape of the steam; and it immediately "become the great highway for the king and occurred to him that the proper application of all his subjects." His first important underthis principle, by increasing the force of the taking was the construction of a railroad 8 fire, would greatly augment the power of the miles in length for the owners of the Hetton boiler to generate steam, and the range and colliery, which, on Nov. 18, 1822, was successcapacity of the engine. Hence originated the fully opened, the level parts being traversed by steam blast

, the most important improvement locomotives, while stationary engines were emin the locomotive made up to that time, which, ployed to overcome the heavy grades. While however, has also been claimed for Hackworth, this work was in progress similar projects beanother inventor. It was embodied in Stephen- gan to be agitated, and in 1820 an act of parson's next engine, completed in 1815; and in liament was obtained for a railway between 1816 he constructed others, greatly simplified Stockton and Darlington, of which Stephenson in the working parts, and which as recently as was appointed engineer at a salary of £300. 1854 formed the model for those employed at The line was intended to be worked by station

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ery engines for the steep gradients, with horse entered, having averaged a speed of 14 miles power on the level portions; but at Stephen- an hour, and even attained a velocity of 29 son's urgent request the act was amended so miles an hour. The “Rocket,” the first highas to permit the use of locomotives on all parts speed locomotive of the standard modern type, of the road, which, at the expiration of some. was distinguished above all preceding ones by what more than 3 years from its commence- 3 elements of efficiency: the multitubular boilment, was formally opened on Sept. 25, 1825, er, which, if not Stephenson's invention, was in the presence of immense throngs of specta- first applied by him to locomotives; the blast tors. The difficulty experienced in procuring pipe; and the direct connection of the steam suitable locomotives from the ordinary black- cylinders to one axle and one pair of wheels. smiths' shops suggested to him the neces- At the ceremony of the opening of the road, sity of establishing a special engine factory, Sept. 15, 1830, Mr. Huskisson, who was in atwhich project was successfully carried into tendance with many other distinguished public effect, with the cooperation of Mr. Pease, the men, having been accidentally struck down and originator of the Stockton road, at Newcastle- fatally injured by this engine, was conveyed upon-Tyne, where some of the most powerful in it from Parkside to Eccles, a distance of 15 steam carriages in the world have since been miles, at the then unprecedented rate of 36 constructed, and many skilled workmen and miles an hour. Having fairly inaugurated the engineers educated. The year 1825 witnessed railway system of England, Stephenson was the production of a multitude of projects for almost incessantly employed for the next 10 railways, of which the Liverpool and Man- years on new roads which were projected in chester line, the most considerable and the all directions, and even visited Belgium and only one seriously supported, was destined to Spain as a consulting engineer. With his inbe not merely the great achievement of Ste- creasing wealth he also engaged extensively phenson's career, but the battle field on which and profitably in coal mining, particularly in were to be fought the momentous questions of the neighborhood of Tapton park, an elegant the superiority of railways to common roads, seat in Derbyshire, where he passed his latof high to low velocities of transport, and of ter years in comfort and peace, beloved by his locomotives to fixed engines. Stephenson made neighbors of every degree and condition, and the preliminary surveys in the teeth of an op- presenting in his conduct, as well as in his position which might have readily disconcert- person and manners, the true ideal of an Enged a less determined spirit; and such were the lish gentleman. He preserved through life ignorance and prejudice of land owners and the simplicity of character which had distintheir agents, who sometimes drove the survey- guished him in youth, and on several occasions ors off their grounds, that much of the work declined the honor of knighthood. Of his had to be done by stealth. An act of parlia- scientific character, Sir J. D. Forbes, who disment having been procured, Stephenson was claims for him any great inventiveness, makes appointed principal engineer, and in June, the following estimate: "His skill rather lay 1826, commenced the construction of the road, in perceiving how far methods and contrivwhich employed him incessantly during the ances already known might be pushed to an next 4 years. Of the engineering difficulties advantageous result. He possessed that shrewd successfully overcome, the most important was decision which ingenious persons often want, the crossing of Chatmoss, a bog 4 miles in enabling him to detect what is truly valuable length, pronounced impassable, on which the in the numerous mechanical schemes which at road was made to float; a feat, as has been ob- any time are afloat, and to devise the means served, “affording an unequivocal proof of that of realizing them. He also possessed that conadmirable self-reliance which never contem- fidence in his own judgment which is necesplates failure.” The patience of Stephenson sary to carry out principles to their legitimate was however destined to be still more severely extent, but from which feebler or more practried; for during the progress of the undertak- tical minds usually shrink.” A memoir of ing the most eminent engineers persisted in George Stephenson, by Samuel Smiles, was recommending stationary engines in place of published in London in 1856.-ROBERT, á raillocomotives, which they declared unsafe and way constructor and engineer, son of the precedincapable of attaining a high degree of speed; ing, born in Willington, near Newcastle-uponand the clumsy expedient of a series of station- Tyne, Dec. 16, 1803, died Oct. 12, 1859. As ary machines 1} miles apart, dragging the a child he evinced remarkable intelligence, and trains by ropes, was seriously entertained, and became in some sort a fellow pupil in several would have been adopted but for the energy branches of knowledge with his father, whose of Stephenson and a few of his friends. He own education was continued far into middle finally prevailed on the directors to offer a life, and whose earnings were long devoted exprize, under certain stipulations, for the most clusively to the instruction of his son. The effective locomotive engine for the purposes latter, who at 12 years of age began to show of the road; and at a trial which took place a decided inclination for mechanics and science, Dear Liverpool, Oct. 6, 1829, his engine, the was, after several years' schooling at Newcas* Rocket," "constructed by himself and his son tle, and a preparatory training in the collieries, Robert, was adjudged to be the best of the 4 sent in 1822 to the university of Edinburgh. He returned home in the succeeding year, and nius not less distinguished than that of his faafter assisting his father in a variety of under- ther. He published a work“On the Locomotakings and perfecting his knowledge of prac- tive Steam Engine,” and another “On the tical mechanics, accepted in 1824, in the hope Atmospheric Railway System.” of benefiting his health, an engagement as STEPPES. See Plains. mining engineer in South America. Recalled STEREOSCOPE (Gr. Otepeos, solid, and by his father in 1827, he was employed in va- OKOTEw, to see), an optical instrument conrious labors connected with the construction trived for combining into one image, which of the Liverpool and Manchester railway, and appears solid, or in relief, two plane represenin the improvement of locomotives; and in tations of a statue, a landscape, or any object 1829 he assisted in designing and making the or field of objects involving three dimensions. successful locomotive, the “Rocket,” which The two separate pictures employed for this was entered in his name. After being engaged purpose are so taken as to show the object or on several minor railway lines, he was appoint- field as it would appear when viewed by each ed engineer of the London and Birmingham of the two eyes separately. Of such pictures, road, which under his direction was completed now known as stereoscopic views, the effect, in 1838; and thenceforth for many years his and hence the preparation, depend on the two time and talents were almost exclusively occu- simple principles, that within certain limits of pied with similar undertakings at home and distance the two eyes see at the same time two abroad. As an engineer he is known by sev- really unlike pictures of any solid object or eral stupendous works designed in immediate field of objects regarded; and that when two connection with railways, among the most re- such pictures (for present purposes considered markable of which are the high level bridge as flat) fall on the retinæ of the corresponding over the Tyne at Newcastle, the viaduct over eyes, the result is a perception of solidity in the Tweed valley at Berwick, the Conway the objects, or of depth in the field, so prebridge, and above all the Britannia tubular sented. If a thin book be held up before the bridge across the Menai straits, 1,850 feet in eyes, with the back toward the face, and looked length and 106 above high water mark, which at with the right eye only, the back and much Sir James Forbes pronounces “a triumph of of the corresponding side are seen, and in a art and science, an honor to his own age, and a certain direction; but on looking with the left lesson to posterity.” In this last undertaking eye only, the image of the book and the plane he received important assistance from Messrs. in which it appears to lie shift slightly toward Hodgkinson and Fairbairn with respect to va- the closed eye, and the back with the other rious points of construction and the strength side now becomes visible. The book presents of materials; but the credit of conceiving the to each eye a somewhat different surface, and enterprise belongs wholly to himself, as well a different position and perspective. On careas the rectangular form of the tube, of which fully regarding it with both eyes, its apparent there had previously been no example in me- position is intermediate to the two before chanical construction. He was also employed found; the back and in a degree both the on railways in Belgium, Norway, Italy, France,' sides are now visible, and the book obviously and other parts of Europe, and visited Egypt stands in relief toward the eyes. several times to superintend the construction pearances, alluded to by Euclid, were more of a road between Alexandria and Cairo, on definitely observed and described by Galen the line of which there are two tubular bridges, about 1,700 years since. The familiar but retraversed by trains on the roof instead of the markable result is, that we neither see objects inside, as in the case of the Britannia bridge. double nor as flat surfaces; but always, when He also designed an immense bridge across the not too far removed, as having depth or reNilo at Kaffre Azzayat. In British North lief, or as existing in a space which shows America he has left a memorable specimen of this third dimension. (See Vision.) A diahis engineering skill and perseverance amid gram expressing to the eye Galen's results was unprecedented difficulties in the great Victoria drawn by Baptista Porta; and from this, about tubular bridge, which crosses the St. Lawrence A. D. 1593, Jacopo Chimenti prepared pairs near Montreal, and was formally opened by of drawings (one pair of which is believed to the prince of Wales in the summer of 1860. be still preserved in a museum at Lille) inIn addition to his railway labors he took con- tended to show persons as seen by the two siderable interest in public affairs, and during eyes separately, and such that, if viewed with the last 12 years of his life represented the the eyes "crossed” by looking at a point nearer Yorkshire borough of Whitby in parliament, to them than are the drawings, so that each where he was known as an able debater on eye receives the image of that which is before subjects connected with the railway interests the other, they are combined, giving a single of the United Kingdom. He was also a mem- image in relief. This method, the “ocular ber of several scientific bodies, and received stereoscope," is still conveniently resorted to, great gold medal of honor from the French in- after some practice, by those who would get dustrial exposition of 1855. His great wealth the stereoscopio effect of views without emwas liberally expended, and he enjoyed a rep- ploying an instrument. Aquilonius (1613) utation for private worth and mechanical ge- wrote a volume on the vision of solid objects,

These ap

in which this principle was introduced. Mr. toward each other, and at the ordinary disHarris (1775) treated on the subject, among tance of the two eyes, about 24 inches apart. other things referring the obviously solid form These are placed in a convenient box, into of the nose as seen by its owner to this effect which the observer looks; while beyond them of vision with two eyes. Prof. Elliott, in 1834, are the slides or double views, which, in case is said to have conceived the plan of an instru- they are opaque, as upon pasteboard, are ment for combining the two single-eye pic- viewed by reflected, or if transparent, as tures, mentioning it to two or three friends, on glass, by transmitted light. A diaphragm, but not carrying it into execution until 1839. extending from in front between and to a litMeanwhile, however, Prof. Wheatstone—to tle way beyond the two semi-lenses, confines whom is unquestionably due the credit of have the vision of each eye to its appropriate picing derised the first effectual and satisfactory ture; while the lenses, refracting laterally instrument for combining two monocular draw- outward to the eyes the light which passes ings or pictures into a solid image, as well as of through them, cause the two images to aphaving distinctly brought before the physicists pear as if originating from a single field beand the public the truth that our actual percep- tween the real places of the views, that is, they tion of solidity depends on the combination of superimpose these; and at the same time their two such visual pictures—had exhibited before effect is to magnify the single resulting image. the royal society in 1838, and also at a meeting The instrument is known as the “lenticular of the British association, his “reflecting stereo- stereoscope.". In the best simple or hand scope," demonstrating its power to unite pairs instruments, the semi-lenses being cut from a of plane geometrical drawings into single and single lens not less than 3 inches in diameter, solid forms. Elliott's device was simply a and set edge to edge, a single wide aperture wooden box, 18 inches long, 7 broad, and 41 serves for both eyes; and the instrument then deep, in the closed or remote end of which suits all eyes without adjustment, and allows the dissimilar pictures were placed. The of an increased field of view.-As no artist can views he first employed were two represent- continually and with certainty execute true ing a leaning cross, with the moon and the pictures of trees, persons, or other near obbranchless stem of a small tree, nearly in line, jects, with just those differences of surface and and as seen from slightly different positions. perspective which they naturally present to No mirrors or lenses are required; but on look- the two eyes separately, it will readily be seen inz into the box, on the "ocular stereoscope" that the stereoscope could be of little use until plan, crossing the eyes, the entire view appears aided by photography. The pictures employed to stand forth in solidity or relief. Wheatstone's must be correct, or their faults are exaggeratarrangement, far superior to this, consists of ed. Public attention seems first to have been two plane mirrors about 4 inches square, so strongly called to the stereoscope as a means of placed as to make each an angle of about 45° amusement and of the improved representation with the axis of the corresponding eye, the of objects, by the fine display of lenticular stertwo mirrors being thus at right angles to each eoscopes and of appropriate photographic views other, and the drawings on separate slips being placed by M. Duboscq in the great exhibition presented, each toward a mirror, at the two at London in 1851.-It is certain that the persides, and at such a distance and angle that ception of solidity or relief, in ordinary vision, the reflected images thrown to the two eyes is in some way connected with the degree of respectively shall appear to have come from a convergence of the axes of the two eyes (the single object at a corresponding distance be- optic axes) toward the object, or the point on hind the mirrors. Thus the two views are in its surface of which at any moment distinct effect superimposed and united, as in natural vision is secured. Though we usually judge rision; and if unlike each other in quite or of distances in a considerable degree, and benearly the same way as when received by the yond a certain limit wholly, by light and shade, eres from the actual object, the latter will be or aërial perspective, by intervening objects, exactly represented, though it may be on a re- and by aid of experience, yet when the objects duced scale, but appearing in solid form, so or their parts are within about 250 to 300 feet, that we seem even to look around and beyond there is a sensible difference in the degree of it. Two pictures of a bust become in effect a convergency of the optic axes, and hence in the solid bust; the waters of a cataract stand forth effort to fix the eyeballs in the required posiin body; a forest, a mountain, or a group of tions, and doubtless therefore in the attending persons comes out in depth, and we look be- muscular sensations. Within some limit, probtween and beyond the individual objects, as ably that named, the degree and character of in the natural view. In 1849 Sir David Brew- these sensations, though unconsciously to him, ster devised a more convenient form of instru- enable the observer to judge of distances; to ment for combining the two pictures, which is determine that some parts of a given object Dow in common use. In this, two convex are nearer, others more remote; and thus, perlenses properly adjusted are employed for haps, during the rapid play of the eyes over viewing the pictures; or more commonly, the object, to obtain that sense of distances parts of a single large double-convex lens, di- which we interpret into solidity of the object. vided in the middle, the thin edges being set For objects about 250 feet away, the optic angle is small, and the sensation of effort slight; persons, the head, or an advanced foot, or the for those much beyond this, both these in ef- dress, is thrown forward to a disagreeable ex. fect vanish, and relief is no longer a perception, tent. This principle, however, becomes useful but only an inference; for distances far within in case of bodies so distant that to the eyes, the limit, the convergency and sensation be- near together as they are, they cannot present come marked. Looking into the stereoscope, the solid form. Remote mountains, buildings, the effort to converge the eyes must be made, &c., flat to ordinary vision, are made to give the sensation of such effort attends, and relief unlike views by placing the cameras many feet is perceived. It may be in this way that two apart, as they would to a person whose visual views of an object a mile distant, and taken by organs could be correspondingly separated; and the double camera in common use, its lenses in the stereoscope such views actually give the little further apart than the eyes, still show re- solid form. This is also the principle of the lief when seen in the instrument; and that, as tele-stereoscope of Helmholtz, in which 4 mirhas been stated, even two flat pictures exactly rors are so placed diagonally, the outer pair alike have in the instrument been made to af- many feet apart, and the inner at the distance ford a view in relief. Brewster argues that to suiting the eyes, that the binocular parallax produce perfect stereoscopic effect, the two or angle between the two lines of sight is greatviews should always be taken through lenses ly enlarged, and distinct relief is secured in obof the double photographic camera, having no jects very remote. The angle made by the more than $ inch diameter, and placed no more axes of the two eyes at the point viewed (the than 2 inches apart, or successively through " optic angle") is, by both the two methods one such lens shifted only to such distance, so last named, in effect greatly enlarged-this anas to answer exactly to the pictures furnished in gle being always a horizontal one-as if the obnature to the two eyes. When there are moving ject were very near; but the visual angle of the objects in the field, and also in taking “instan- object, usually regarded especially in the vertitaneous views," so called, the double camera cal direction, remaining just what it would be becomes requisite, or two single cameras, sta- with the ordinary base between the eyes, the tioned at suitable distance and acting togeth- result is that the judgment of the observer is er. For stationary objects the single camera deceived, and, unless proportionate magnifying is conveniently used, the pictures being taken power of lenses be employed, the object appears in succession. In taking stereoscopic pictures, actually diminished in size. The principle of it has been customary (though probably the increased distance between stations is availed tendency is now back toward the natural con- of in taking stereoscopes of the moon, as has ditions) to exaggerate the effect both in respect been done by L. M. Rutherfurd of New York, to distance between stations and to the size of and by W. De la Rue of London. At differlens. When the plates used are less sensitive, ent seasons the moon presents slightly different larger lenses may be employed to accelerate faces toward the earth; and two views taken the process; sometimes those of 2, 3, or 4 from positions in the earth's orbit 15o apart, inches diameter. So a broad base or distance and placed in the stereoscope, give a perfect between stations of the camera is resorted to and beautiful globe, its surface diversified with for the purpose of exaggerating the relief; for the well known lights and shades of that lnnear persons or statues, sometimes as much as minary. M. Claudet, of London, has devised a 6 to 8 inches; for landscapes, 10 to 20 inches, method in which relief is secured by means of or even several feet. Thus, strongly differing the image of a single picture or object thrown sides, perspectives, or projections of the objects on a ground glass screen, hence termed a stereoare obtained. In the double camera, the tubes monoscope. In this case it is asserted that through which light enters, to be thrown by a the image in relief is visible to several spectaconvex lens in each on the prepared plates, are tors at the same time. Another method, by not parallel, but inclined to each other at a Mr. Maugham, applies glasses of complemencertain angle, which is usually less in the cam- tary colors, say green and red, to the rays eras for taking portraits than in those for views. which are thrown by a magic lantern on the But in taking the photographic visiting cards, screen, and corresponding glasses to the two by 4 parallel tubes directed toward the person eyes of each observer, in order to keep sepaand view at the same time, 4 pictures are ob- rate the rays of the two images; but much tained; then, without shifting the person or light is in this way lost, and the image is faint. instrument, 4 others upon another portion of Mr. Thomas Skaife, of Blackheath, England, the same slide ; and it is unexpectedly found using a small thin lens, of 1 inch focus, has obthat of these, any right-hand image being tained almost instantaneous views which, when suitably placed in the stereoscope with any magnified, are still extremely well defined and left-hand image, perfect relief is the result. perfect, and which he has termed pistolographs. With near objects, a long base line and marked Enclosed between two plates of glass, and the difference of perspective result in distorting three semi-fused into one, one of these miniathe objects in the direction from before back- ture pictures retains its beauty, while it is proward (that of depth); all streets, buildings, tected and preserved; the combination he has and similar views extending away from the termed the chromo-crystal. It is stated that eye, appear disproportionately long; and in Mr. John Sang, of Kirkcaldy, has recently, by

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