Moreover, these chemical influences of light give birth to the whole vegetable world, with all its varied charms of colour, form, and property, and, as we have seen in the last Chapter, on them animal life itself depends.

The conclusions arrived at in optics necessarily entered as Of heat: reflection, fundamental ideas in thermotics, or the science of heat; for refraction. radiant heat moves also in straight lines, undergoes reflection, refraction, double refraction, polarization, and hence the theory of transverse vibrations applies to it. Heat is invisible light, as light is visible heat. Correct notions of radiation originated with the Florentine academicians, who used concave mirrors; and, in the cold-ray experiment, masses of ice of five hundred pounds' weight. The refraction of invisible heat was ascertained in consequence of the invention of the thermo-electric pile. It polarization and depolarization soon followed. Already had been demonstrated the influence of the physical state of radiant surfaces, and that the heat comes also from a little depth beneath them. The felicitous doctrine of exchanges of Exchanges heat imparted true ideas of the nature of calorific equilibrium and the heating and cooling of bodies, and offered an explanation of many phenomena, as, for instance, the formation of dew, This deposit of moisture occurs after sunset, the more copiously The dew, the clearer the sky; it never appears on a cloudy night; it of. neither ascends from the ground like an exhalation, nor descends like a rain. It shows preferences in its manner of settling, being found on some objects before it is on others. All these singular peculiarities were satisfactorily explained, and another of the mysteries, the unaccountable wonders of the Middle Ages, brought into the attitude of a simple physical fact.

of heat.

the nature

cence.

It is impossible, in a limited space, to relate satisfactorily Incandeswhat has been done respecting ignition, the production of light by incandescence, the accurate measurement of the conductibility of bodies, the determination of the expansions of solids, liquids, gases, under increasing temperature, the variations of the same substance at different degrees, the heat of fluidity and elasticity, and specific heat, or to do justice to the great improvements made in all kinds of instruments,-ba

struments.

Effect of

mechanical

Physical in- lances, thermometers, contrivances for linear and angular measures, telescopes, microscopes, chronometers, aerostats, telegraphs, and machinery generally. The tendency in every direction has been to practical applications. More accurate knowledge implies increasing power, greater wealth, higher virtue. The morality of man is enhanced by the improvement of his intellect and by personal independence. Our age has become rational, industrial, progressive. In its great physical inventions. inventions Europe may securely trust. There is nothing more to fear from Arabian invasions or Tartar irruptions. The hordes of Asia could be swept away like chaff before the wind. Let him who would form a correct opinion of the position of man in the present and preceding phases of his progress reflect on the losses of Christendom in Asia and Africa, in spite of all the machinery of an Age of Faith, and the present security of Europe from every barbarian or foreign attack.

Illustration from the

nufacture.

From almost any of the branches of industry facts might be presented illustrating the benefits arising from the application of physical discoveries. As an example, I may refer to the cotton manufacture.

In a very short time after the mechanical arts were applied cotton ma- to the manufacture of textile fabrics, so great was the improvement that a man could do more work in a day than he had previously done in a year. That manufacture was moreover accompanied by such collateral events as actually overturned the social condition throughout Europe. These were such as the invention of the steam-engine, the canal system, the prodigious developement of the iron manufacture, the locomotive, and railroads; results not due to the placemen and officers to whom that continent had resigned its annals, whose effigies encumber the streets of its cities, but to men in the lower walks of life. The assertion is true that James Watt, the instrument maker, conferred on his native country more solid benefits than all the treaties she ever made and all the battles she ever won. Arkwright was a barber, Harrison a carpenter, Brindley a millwright's apprentice.

By the labours of Paul or of Wyatt, who introduced the

Of Mechanical Inventions.

ment of the

manufac

373 operation of spinning by rollers, a principle perfected by Ark- Developewright; by the rotating carding-engine, first devised by Paul; cotton by the jenny of Highs or Hargreaves; the water-frame; the ture in mule invented by Crompton,-so greatly was the cotton manu- England. facture developed as to demand an entire change in the life of operatives, and hence arose the factory system. At a critical moment was introduced Watt's invention, the steam-engine. His first patent was taken out in 1769, the same year that Arkwright patented spinning by rollers. Watt's improve- The steamment chiefly consisted in the use of a separate condenser, and Watt. the replacement of atmospheric pressure by that of steam. Still, it was not until more than twenty years that this engine was introduced into factories, and hence it was not, as is sometimes supposed, the cause of their wonderful increase. It came, however, at a fortunate time, nearly coincident with the invention of the dressing-machine by Radcliffe and the powerloom by Cartwright,

engine of

by chlorine.

If the production of textile fabrics received such advantages Bleaching from mechanics, equally was it favoured by chemistry in the discovery of bleaching by chlorine. To bleach a piece of cotton by the action of the air and the sun required from six to eight months, and a large surface of land must be used as a bleach-field. The value of land in the vicinity of great towns presented an insuperable obstacle to such uses. By chlorine the operation could be completed in the course of a few hours, and in a comparatively small building, the fibre being beautifully and permanently whitened. Nor were the chemical improvements restricted to this. Calico-printing, an art prac- Calicoprinting by tised many thousand years ago among the Egyptians, was cylinders. • perfected by the operation of printing from cylinders.

It deserves to be remarked that the cotton manufacture was first introduced into Europe by the Arabs. Abderrahman III., A.D. 930, caused it to be commenced in Spain; he also had extensive manufactures of silk and leather, and interested himself much in the culture of the sugar-cane, rice, the mulberry. One of the most valuable Spanish applications of cotton was in the invention of cotton-paper. The Arabs were also the authors of the printing of calicoes by wooden blocks,

Extent of the cotton manufacture.

ments in

canals.

a great improvement on the old Indian operation of painting by hand.

We may excuse the enthusiastic literature of the cotton manufacture its boasting, for men had accomplished works that were nearly God-like. Mr. Baines, writing in 1833, states that the length of yarn spun in one year was nearly five thousand millions of miles, sufficient to pass round the earth's circumference more than two hundred thousand times,-sufficient to reach fifty-one times from the earth to the sun. It would encircle the earth's orbit eight and a half times. The wrought fabrics of cotton exported in one year would form a girdle for the globe passing eleven times round the equator, more than sufficient to form a continuous sheet from the earth to the moon. And if this was the case thirty years ago, by what illustrations would it be possible to depict it, now (1859) when the quantity of cotton imported by England alone is more than twelve hundred millions of pounds?

Improve- But such a vast developement in that particular manufacture locomotion. necessarily implied other improvements, especially in locomotion and the transmission of intelligence. The pedlar's pack, the pack-horse, and the cart became altogether inadequate, and, in succession, were replaced by the canal system of the last century, and by the steamboats and railroads of this. Brindley's The engineering triumphs of Brindley, whose canals were carried across valleys, over or through mountains, above rivers, excited unbounded admiration in his own times, and yet they were only the precursors of the railway engineering of ours. As it was, the canal system proved to be inadequate to the want, and oaken railways, which had long been used in quarries and coalpits, with the locomotive invented by Murdoch in Stephen- 1784, were destined to supplant them. It does not fall within my present purpose to relate how the locomotion of the whole civilized world was revolutionized, not by the act of some mighty sovereign or soldier, but by George Stephenson, once a steam-engine stoker, who, by the invention of the tubular boiler and the ingenious device of blowing the chimney instead of the fire, converted the locomotive of the last century, which, at its utmost speed, could only travel seven miles an

son's loco

tives.

way system.

hour, into the locomotive of this, which can accomplish seventy. I need not dwell on the collateral improvements, the intro- The railduction of iron for rails, metallic bridges, tubular bridges, viaducts, and all the prodigies of the existing system of railway engineering.

ment in the

tion of ma

It is not only on account of the gigantic nature of the work Improveit has to execute that the machinery employed in the great construcmanufactures, such as those of cotton and iron, is so worthy chinery. of our admiration; improvements as respects the correctness, and even the elegance of its own construction, attract our attention. It has been truly said of steam-engines that they were never properly made until they made themselves. In any machine, the excellence of its performance depends on the accuracy of its construction. Its parts must be made perfectly true, and, to work smoothly, must work without error. To accomplish such conditions taxed to its utmost the mechanical ingenuity of the last century; and, indeed, it was not possible to reach perfect success so long as the hand alone was resorted to. Work executed by the most skilful mechanic could be no more than approximately correct. Not until such machines as the sliding rest and planing engine were introduced could any approach to perfection be made. Improvements of this nature reacted at once on the primary construction of machinery, making it more powerful, more accurate, more durable, and also led to the introduction of greater elegance in its planning or conception, as any one may see who will compare the clumsy, half-wood half-metal machinery of the last century with the light and tasteful constructions of this.

While thus the inventive class of men were gratifying their Social changes mental activity, and following that pursuit which has ever en- effected by machinery. grossed the energetic in all ages of the world,-the pursuit of riches; for it was quickly perceived that success in this direction was the high-road to wealth, public consideration, and honour, the realization of riches greater than the wildest expectations of the alchemists, there were silently and in an unobserved manner great social and national results arising. The operative was correct enough in his conclusion that ma