The effect of continued violent bodily exertion upon the duration of life might be illustrated by many instances; we shall mention one. The late Mr. Edgeworth, in his Memoirs, repeatedly speaks of a boatman whom he knew at Lyons, as an old man. "His hair," says Mr. Edgeworth, "was grey, his face wrinkled, his back bent, and all his limbs and features had the appearance of those of a man of sixty; yet his real age was but twenty-seven years. He told me that he was the oldest boatman on the Rhone, that his younger brothers had been worn out before they were twenty-five years old; such were the effects of the hardships to which they were subject from the nature of their employment." That employment was, by intense bodily exertion, and with the daily chance of being upset, to pull a boat across one of the most rapid rivers in the world,-- "The swift and arrowy Rhone," as one of our poets calls it. How much happier would these boatmen have been during their lives, and how much longer would they have lived, could their labour have been relieved by some mechanical contrivance! and without doubt, the same contrivance would have doubled the number of boatmen, by causing the passage to be more used. As it was, they were few in number, they lived only a few years, and the only gratification of those few years was an inordinate stimulus of brandy. This is the case in all trades where immense efforts of bodily power are required. The exertion itself wears out the people, and the dram, which gives a momentary impulse to the exertion, wears them out still more. The coal-heavers of London, healthy as they look, are but a short-lived people. The heavy loads which they carry, and the quantity of liquor which they drink, both together make sad havoc with them. Violent bodily labour, in which the muscular power of the body is unequally applied, generally produces some peculiar disease. Nearly all the pressmen who were accustomed to print newspapers of a large size, by hand, were ruptured. The printing-machine now does the same description of work.