to an instant when we shall overtake him, and tread in his footsteps. This new-born giant thrusteth his iron arm into the bowels of the earth, and throws up its treasures by thousands of tons, emptying the dark mine of its wealth, then leaping on the surface, melting with its hot breath the weighty metal, and rolling and beating it out into massy bars, or drawing it through its crushing fingers until it becomes almost as thin as a lady's girdle. As if struck by the wand of a magician, the iron vessel springs out of the shapeless mass of ore, by the power of steam is launched upon the deep, and stands, as if in mockery, beside its oak-built rival, every rib of which was the growth of a long century. The very leaves that rustle in our hand while we read were formed by it, and every letter in the large sheet of news bears the imprint of its majestic footstep. Even printing, the grandest of all human inventions, was but in comparison the slow copying of the clerk, beside this ready-writer, which now throws off its thousands of perfect impressions within the brief space of a single hour. It grinds the bread we eat, and gives all the variety and beauty to the garments we wear. It stamps the wreath of flowers upon the flimsy foundation of cotton, and sets ten thousand wheels in motion, every stroke of which would grind the human form to powder. And yet the whole of this moving destruction can be stopped in a moment by the hand of a child, when once shown where to place its tiny fingers. The invention of Printing gave power to the human mind to achieve new triumphs over ignorance and vice, and by means of the steamengine every element of Nature, wherein opposition seemed ever ready to spring forth and defy or overwhelm man, is now bound and overpowered.

Yet, while contemplating the grandeur of the discovery, we are humbled, as in the instance of other great inventions, by the remembrance that so many centuries of human history have passed away during which the powers of steam-an

element almost perpetually within the observation of men— were, although perceived, unemployed. "What might the world have become, by this time, had the wonderful capabilities of steam been known to the nations of antiquity!" is a natural exclamation; but reflection on the nature of man, and his slow advancement in the great path of fact and science, will, at once, hush the expression of our wondering regret over the Past,-while a nobler and more cheering occupation for the mind, offers itself in speculation on the glorious Future. Let us attend to the history of this all important invention, as a means of assisting our calculations of the mighty issues of that civilization which is now begun.

But in order to understand aright the beautiful simplicity of the means by which such great changes have been wrought in the world, it is necessary to explain what steam is, and the manner in which it acts in propelling the ingenious machines to which it is applied.

Every one has seen a common tea-kettle upon the fire, with a white stream of vapour pouring from the spout, and most people have also observed that the more furiously the water boils, the more energetically the stream of vapour pours forth. This is the natural result of the application of heat to water, for as the bottom of the vessel, which is nearest the water, first feels the effects of the heat, those effects are next communicated to the water immediately near to it. As this grows warm the heat is communicated to the next globules, and so the process goes on until it is diffused through the whole quantity of water. As that grows hotter and hotter at the bottom of the vessel, particles expand until they assume the form of vapour; and these being lighter than the water, gradually force their way through the globules at the sides, until they reach the surface, where they are partially condensed into water again, and partly remain in the condition of vapour, unable to overcome the resistance of the atmosphere,

which presses, with a weight of fifteen pound on the square inch, above them. As the number of these vaporous globules increases, the sound of their propulsion against the globules of air accumulates until it becomes audible at a little distance, and then we hear what is called singing.

As the heat still continues to be applied to the water, this expansion of it gradually increases until it is diffused through the whole body in the vessel, and the disturbance is shown in the upheaving and tumultuous agitation of the surface, and the water appears in a state of ebullition, or is what we call boiling. As the boiling goes on, the number of globules of water which are expanded into steam increase so much that the force overcomes the weight of the superincumbent atmosphere, and the steam pours forth.

In Dr. Lardner's valuable work on the steam-engine he furnishes us with the following interesting examples of the motive power of a pint of water, when converted by the consumption of two ounces of coal into steam :— "A pint of water," he informs us, 66 may be evaporated by two ounces of coals. In its evaporation it swells into two hundred and sixteen gallons of steam, with a mechanical force sufficient to raise a weight of thirty-seven tons a foot high. The steam thus produced has a pressure equal to that of common atmospheric air; and by allowing it to expand, by virtue of its elasticity, a further mechanical force may be obtained, at least equal in amount to the former. A pint of water, therefore, and two ounces of common coal, are thus rendered capable of doing as much work as is equivalent to seventy-four tons raised a foot high."

In relation to the consumption of fuel Dr. Lardner observes:-" The circumstances under which the steam-engine is worked on a railway are not favourable to the economy of fuel. Nevertheless, a pound of coke burned in a locomotive engine will evaporate about five pints of water. In their

evaporation they will exert a mechanical force sufficient to draw two tons weight on the railway a distance of one mile in two minutes. Four horses working in a stage-coach on a common road are necessary to draw the same weight the same distance in six minutes.

"A train of coaches weighing about eighty tons, and transporting two hundred and forty passengers with their luggage, has been taken from Liverpool to Birmingham, and back from Birmingham to Liverpool, the trip each way taking about four hours and a quarter, stoppages included. The distance between these places by the railway is ninety-five miles. This double journey of one hundred and ninety miles is effected by the mechanical force produced in the combustion of four tons of coke, the value of which is about five pounds. To carry the same number of passengers daily between the same places by stage-coaches on a common road, would require twenty coaches and an establishment of three thousand eight hundred horses, with which the journey in each direction would be performed in about twelve hours, stoppages included.

"The circumference of the earth measures twenty-five thousand miles; and if it were begirt with an iron railway, such a train as above described, carrying two hundred and forty passenger, would be drawn round it by the combustion of about thirty tons of coke, and the circuit would be accomplished in five weeks.

"In the drainage of the Cornish mines the economy of fuel is much attended to, and coals are there made to do more work than elsewhere. A bushel of coals usually raises forty thousand tons of water a foot high; but it has on some occasions raised sixty thousand tons the same height. Let us take its labour at fifty thousand tons raised one foot high. A horse worked in a fast stage-coach pulls against an average resistance of about a quarter of a hundredweight. Against this he is able to work at the usual speed through about

eight miles daily; his work is therefore equivalent to one thousand tons raised one foot. A bushel of coals consequently, as used in Cornwall, performs as much labour as a day's work of one hundred such horses.

“The great pyramid of Egypt stands upon a base measuring seven hundred feet each way, and is five hundred feet high, its weight being twelve thousand seven hundred and sixty millions of pounds. Herodotus states, that in constructing it one hundred thousand men were constantly employed for twenty years. The materials of this pyramid would be raised from the ground to their present position by the combustion of about four hundred and eighty tons of coals.

"The Menai bridge consists of about two thousand tons of iron, and its height above the level of the water is one hundred and twenty feet. Its mass might be lifted from the level of the water to its present position by the combustion of four bushels of coals."

It may cause the reader some surprise to be informed that the discovery of the fact that a mechanical force is produced when water is evaporated by the application of heat (the first capital step in the invention of the steam-engine), is very nearly two thousand years old, having been first pointed out by Hero of Alexandria one hundred and twenty years before the Christian Era. Our young reader will doubtless regard it as almost an equal matter for surprise that this important discovery should have slumbered, as it were, for nearly seventeen hundred years before any application of it to practical uses was attempted, and for upwards of another hundred years before such application even to the most limited extent proved successful. It was about a century and a half ago that a steamengine, constructed on an imperfect principle, was first used for the raising of water out of mines, which, though much improved upon during the next eighty years, was not sought to be applied other purpose. It is from the time of the grand discoveries

to any