Coulomb has furnished the most accu rate and varied observations on the mea sure of human labor. A man will climb a stair, of from 70 to 100 feet high, at the rate of 45 feet in a minute. Reckoning his weight at 155 lbs., the animal exer tion for one minute is 6975 lbs., and would amount to 4,185,000, if continued for 10 hours. A person may clamber up a rock 500 ft. high, by a ladder-stair, in 20 minutes, and, consequently, at the rate of 25 feet each minute ; his efforts are thus already impaired, and the perfor mance reaches only 3875 in a minute. But, under the incumbrance of a load, the quantity of action is still more re markably diminished. A porter, weigh ing 140 lbs., was found willing to climb a stair, 40 ft. high, 266 times in a day ; but he could carry up only 66 loads of firewood, each of them 168 lbs. weight. In the former case, his daily performance was very nearly 1,500,000 ; while, in the latter, it amounted only to 808,000.
The quantity of permanent effect was hence only about 700,000, or scarcelyhalf the labor exerted in mere climbing. In the driving of piles, a load of 42 lbs., called the ram, is drawn up 38 ft. high 20 times in a minute ; but the work has been considered so fatiguing, as to endure only three hours a day. This gives about 580,000 for the daily performance. Near ly the same result is obtained by comput ing the quantity of water, which, by means of a double bucket, a man drew up from a well. He lifted 86 lbs. 120 times in a day, from a depth of 120 ft., the total effect being 518,400. A skilful laborer, working in a field with a large hoe, creates an effect equal to 728,000. When the agency of a winch is employed in turning a machine, the performance is still greater, amounting to 845,000. In all these instances, a certain weight is heaved up, but a much smaller effort is sufficient to transport a load horizontally.
A man could, in the space of a day, scarcely reach an altitude of two miles, by climbing up a stair, though he will easily walk over 30 miles, on a smooth and level road. But he would, in the same time, carry 130 lbs. only to the fourth part of that distance, or 7} miles. Assuming his own weight to be
140 lbs., the quantity of horizontal action would amount to 42,768,000, or 28 times the vertical performance ; but the share of it, in conveying the load, is 20,961,780, or about 30 times what was spent in ite elevation. The greatest advantage is ob tained by reducing the burthen to 102 lbs., the length of journey being augmented in a higher ratio.
According to some experiments of the late Mr. Buchanan, the exertions of a man in working a pump, in turning a winch, in ringing a bell, and in rowing a boat, are as the numbers 100, 167, 227, and 248.
A man's force, in fact, is such, that he can raise 10 lbs. 10 ft. in a second, for 10 hours in a day, or 100 lbs., or 10 imperial gallons, 1 ft, per second, or in 10 hours, (36,000 seconds) 8,600,000 lbs. one ft., or 360,000 gallons one ft.
The labor of a horse in a day is com monly reckoned equal to that of five men ; but then he works only eight hours, while a man easily continues his exertions for ten hours. Horses, like wise, display much greater force in carry ing than in pulling ; and yet an active walker will beat them on a long journey. Their power of drawing seldom exceeds 144 lbs., but they are capable of carrying more than six times as much weight. With regard to the ordinary power of draught, the formula where s denotes the velocity in miles an hour, will perhaps be found sufficiently nee, the truth. Thus, a horse beginning hit pull with the force of 144 lbs., would draw 100 lbs. at a walk of two miles an hour, but only 64 lbs. when advancing al double that rate, and not more than 31 lbs. if he quickened his pace to six miles an hour. His greatest performance would hence be made with the velocity of 4 miles an hour. The accumulated effort in a minute will then amount to 22,528. The measure generally adopted for computing the power of steam-en gines is much higher, the labor of a horse being reckoned sufficient to raise, every minute, to the elevation of one the weight of 32,000 lbs. Wheel-carriages enable horses, on level roads, to draw, at an average, loads about 15 times greater than the power exerted.