The extension of the railway system is one of the wonders of our time. The few score miles of railroad planted in 1825 have put forth offshoots and branches, till now a mighty net-work of some ten thousand miles in all, is spread over the three kingdoms, with many fresh shoots in bud. Up to the end of 1834, when not a hundred miles of railway were open, the annual average of travellers by coach was some six millions a year; ten years afterwards there were more than four times that number, and to-day the annual average is more than a hundred millions! The number of persons employed upon the working railroads of the United Kingdom amount to about one hundred and thirty thousand, while nearly half as many find employment in the construction of new lines. A few facts, stated by the late Mr. Robert Stephenson, illustrate in a very striking manner the gigantic proportion of the railway system of Great Britain:--The railway has pierced the earth with tunnels to the extent of more than fifty miles, and there are about twelve miles of viaducts in the vicinity of London alone. The earthworks which have been thrown up would measure 550,000,000 cubic yards, beside which St. Paul's would shrink to a pigmy, for it would form a pyramid a mile and a half high, with a base larger than the whole of St. James's Park. Every moment four tons of coal flashes into steam twenty tons of water--as much water as would suffice to supply the domestic and other wants of a town the size of Liverpool, and as much coal as equals half the consumption of the metropolis. The wear and tear is so great that twenty thousand tons of iron have to be replaced annually, and three hundred thousand trees, or as much as five thousand acres could produce, have to be felled for sleepers.