If, early on a summer morning before the smoke of countless fires had narrowed the horizon of the metropolis, a spectator were to ascend to the top of St. Paul's, and take his stand upon the balcony, that with gilded rail flashes like a fringe of fire upon the summit of the dome, he would see sleeping beneath his feet the greatest camp of men upon which the sun has ever risen. As far as he could distinguish by the morning light he would behold stretched before him the mighty map of the metropolis; and could he ascend still higher, he would note the stream of life overflowing the brim of hills which enclose the basin in which it stands. In the space swept by his vision would lie the congregated habitations of two millions and a half of his species--but how vain are figures to convey an idea of so immense a multitude. If Norway, stretching from the Frozen Ocean down to the southern extremity of the North Sea, were to summon all its people to one vast conclave, they would number little more than half the souls within the London bills of mortality. Switzerland, in her thousand valleys, could not muster such an army; and even busy Holland, within her mast-thronged harbours, humming cities, and populous plains, could barely overmatch the close-packed millions within sound of the great bell at his feet. As the spectator gazed upon this extraordinary prospect, the first stir of the awakening city would gradually steal upon his ear. The rumbling of wheels, the clang of hammers, the clear call of the human voice, all deepening by degrees into a confused hum, would proclaim that the mighty city was once more rousing to the labour of the day, and the blue columns of smoke climbing up to heaven that the morning meal was at hand. At such a moment the thought would naturally arise in his mind,--In what manner is such an assemblage victualled? By what complicated wheels does all the machinery move by which two millions and a half of human beings sit down day by day to their meals as regularly and quietly as though they only formed a sung little party at Lovegrove's on a summer's afternoon? As thus he mused respecting the means by which the supply and demand of so vast a multitude is brought to agree, so that every one is enabled to procure exactly what he wants, at the exact time without loss to himself or injury to the community, thin lines of steam, sharply marked for the moment, as they advanced one after another from the horizon and converged towards him would indicate the arrival of the great commissariat trains, stored with produce from all parts of these isles and from the adjacent continent. Could his eye distinguish in addition the fine threads of that far-spreading web which makes London the most sensitive spot on the earth, he would be enabled to take in at a glance the two agents--steam and electricity--which keep the balance true between the wants and the supply of London.