STRENGTH, in physiology, the same with force.
Men may apply their strength several ways in working a machine. A man of ordinary strength, turning a roller by the handle, can act for a whole day against a resistance equal to thirty pounds weight : and if he works ten hours a day, he will raise a weight of thirty pounds through three feet and a half in a second of time: or if the weight be greater, he will raise it so much ices in proportion. But a man may act, for a small time, against a resistance of fifty pounds or more. If two men work at a windlass, or roller, they can more espily draw up se venty pounds, than one man can thirty pounds, provided the elbow of one of the handles be at right angles to that of the other. And with a fly, or heavy wheel, applied to it, a man may do one third part more work ; and for a little while lie can act with a force, or overcome a continual resistance, of eighty pounds : and work a whole day when the resist ance is but forty pounds. Men used to bear loads, such as porters, will carry, some one hundred and fifty pounds, others two hundred or two hundred and fifty pounds, according to their strength. A man can draw but about seventy or eighty pounds horizontally : for he can but apply about half his weight. If the weight of a man be one hundred and forty pounds, he can act with no great er force in thilisting horizontally, at the height of his shoulders, than twenty-se ven pounds.
As to horses ; a horse is, generally speaking, as strong as five men. A horse will carry two hundred and forty, or two hundred and seventy pounds, A horse draws to greatest advantage, when the line of direction is a little elevated above the horizon, and the power acts against his breast : and he can draw two hundred pounds for eight hours a day, at two miles and a half an hour. If he draw two hun dred and forty pounds, he can work but six hours, and not go quite so fast. And in both cases, if he carries some weight, be will draw the better for it, and this is The weight a horse is supposed to be able to draw over a pulley out of a well. But in a cart a horse may draw one thousand pounds, or even double that weight, or a ton weight, or more. As the most force a horse can exert is when he draws a little above the horizontal position, so the worst way of applying the strength of a horse is, to make him carry or draw up hill : and three men on a steep bill, carrying each one hundred pounds, will climb up faster than a horse with three hundred pounds. Also, though a horse may draw in a round walk of eighteen feet diameter ; yet such a walk should not be less than twenty-five or thirty feet diameter.