Part 16 (2/2)

The changes which have been outlined produced the now typical American locomotive. It was necessarily given such form that it would work safely and efficiently on rough, ill-ballasted, and often sharply-winding tracks; and thus it soon became evident that the two pairs of coupled driving-wheels, carrying two-thirds the weight of the whole engine, the forward-truck, and the system of ”equalizing”

suspension-bars, by which the weight is distributed fairly among all the wheels, whatever the position of the engine, or whatever the irregularity of the track, made it the very best of all known types of locomotive for the railroads of a new country. Experience has shown it equally excellent on the smoothest and best of roads. The ”cow-catcher,” placed in front to remove obstacles from the track, the bell, and the heavy whistle, are characteristics of the American engine also. The severity of winter-storms compelled the adoption of the ”cab,” or house, and the use of wood for fuel led to the invention of the ”spark-arrester” for that cla.s.s of engines. The heavy grades on many roads led to the use of the ”sand-box,” from which sand was sprinkled on the track, to prevent the slipping of the wheels.

In the year 1836, the now standard chilled wheel was introduced for cars and trucks; the single eccentric, which had been, until then, used on Baldwin engines, was displaced by the double eccentric, with hooks in place of the link; and, a year later, the iron frame took the place of the previously-used wooden frame on all engines.

The year 1837 introduced a period of great depression in all branches of industry, which continued until the year 1840, or later, and seriously checked all kinds of manufacturing, including the building of locomotives. On the revival of business, numbers of new locomotive-works were started, and in these establishments originated many new types of engine, each of the more successful of which was adapted to some peculiar set of conditions. This variety of type is still seen on nearly all of the princ.i.p.al roads.

The direction of change in the construction of locomotive-engines at the period at which this division of the subject terminates is very well indicated in a letter from Robert Stephenson to Robert L.

Stevens, dated 1833, which is now preserved at the Stevens Inst.i.tute of Technology. He writes: ”I am sorry that the feeling in the United States in favor of light railways is so general. In England we are making every succeeding railway stronger and more substantial.” He adds: ”Small engines are losing ground, and large ones are daily demonstrating that powerful engines are the most economical.” He gives a sketch of his latest engine, weighing _nine tons_, and capable, as he states, of ”taking 100 tons, gross load, at the rate of 16 or 17 miles an hour on a level.” To-day there are engines built weighing 70 tons, and our locomotive-builders have standard sizes guaranteed to draw over 2,000 tons on a good and level track.

[Ill.u.s.tration]

CHAPTER V.

_THE MODERN STEAM-ENGINE._

”Voila la plus merveilleuse de toutes les Machines; le Mecanisme ressemble a celui des animaux. La chaleur est le principe de son mouvement; il se fait dans ses differens tuyaux une circulation, comme celle du sang dans les veines, ayant des valvules qui s'ouvrent et se ferment a propos; elles se nourrit, s'evacue d'elle meme dans les temps regles, et tire de son travail tout ce qu'il lui faut pour subsister. Cette Machine a pris sa naissance en Angleterre, et toutes les Machines a feu qu'on a construites ailleurs que dans la Grande Bretagne ont ete executees par des Anglais.”--BELIDOR.

THE SECOND PERIOD OF APPLICATION--1800-1850 (CONTINUED). THE STEAM-ENGINE APPLIED TO s.h.i.+P-PROPULSION.

Among the most obviously important and most inconceivably fruitful of all the applications of steam which marked the period we are now studying, is that of the steam-engine to the propulsion of vessels.

This direction of application has been that which has, from the earliest period in the history of the steam-engine, attracted the attention of the political economist and the historian, as well as the mechanician, whenever a new improvement, or the revival of an old device, has awakened a faint conception of the possibilities attendant upon the introduction of a machine capable of making so great a force available. The realization of the hopes, the prophecies, and the aspirations of earlier times, in the modern marine steam-engine, may be justly regarded as the greatest of all the triumphs of mechanical engineering. Although, as has already been stated, attempts were made at a very early period to effect this application of steam-power, they were not successful, and the steams.h.i.+p is a product of the present century. No such attempts were commercially successful until after the time of Newcomen and Watt, and at the commencement of the nineteenth century. It is, indeed, but a few years since the pa.s.sage across the Atlantic was frequently made in sailing-vessels, and the dangers, the discomforts, and the irregularities of their trips were most serious.

Now, hardly a day pa.s.ses that does not see several large and powerful steamers leaving the ports of New York and Liverpool to make the same voyages, and their pa.s.sages are made with such regularity and safety, that travelers can antic.i.p.ate with confidence the time of their arrival at the termination of their voyage to a day, and can cross with safety and with comparative comfort even amid the storms of winter. Yet all that we to-day see of the extent and the efficiency of steam-navigation has been the work of the present century, and it may well excite our wonder and our admiration.

The history of this development of the use of steam-power ill.u.s.trates most perfectly that process of growth of this invention which has been already referred to; and we can here trace it, step by step, from the earliest and rudest devices up to those most recent and most perfect designs which represent the most successful existing types of the heat-engine--whether considered with reference to its design and construction, or as the highest application of known scientific principles--that have yet been seen in even the present advanced state of the mechanic arts.

The paddle-wheel was used as a subst.i.tute for oars at a very early date, and a description of paddle-wheels applied to vessels, curiously ill.u.s.trated by a large wood-cut, may be found in the work of Fammelli, ”De l'artificioses machines,” published in old French in 1588.

Clark[58] quotes from Ogilby's edition of the ”Odyssey” a stanza which reads like a prophecy, and almost awakens a belief that the great poet had a knowledge of steam-vessels in those early times--a thousand years before the Christian era. The prince thus addresses Ulysses:

[58] ”Steam and the Steam-Engine.”

”We use nor Helm nor Helms-man. Our tall s.h.i.+ps Have Souls, and plow with Reason up the deeps; All cities, Countries know, and where they list, Through billows glide, veiled in obscuring Mist; Nor fear they Rocks, nor Dangers on the way.”

Pope's translation[59] furnishes the following rendering of Homer's prophecy:

[59] ”Odyssey,” Book VIII., p. 175.

”So shalt thou instant reach the realm a.s.signed, In wondrous s.h.i.+ps, self-moved, instinct with mind;

Though clouds and darkness veil the enc.u.mbered sky, Fearless, through darkness and through clouds they fly.

Though tempests rage, though rolls the swelling main, The seas may roll, the tempests swell in vain; E'en the stern G.o.d that o'er the waves presides, Safe as they pa.s.s and safe repa.s.s the tide, With fury burns; while, careless, they convey Promiscuous every guest to every bay.”

It is stated that the Roman army under Claudius Caudex was taken across to Sicily in boats propelled by paddle-wheels turned by oxen.

Vulturius gives pictures of such vessels.

This application of the force of steam was very possibly antic.i.p.ated 600 years ago by Roger Bacon, the learned Franciscan monk, who, in an age of ignorance and intellectual torpor, wrote:

<script>