HORSE POWER. It is well known among engineers that a horse is capable of raising a weight of about 150 lb. 220 feet high in a minute, and to continue exertions enabling him to do that for 8 hours a-day.
Multiply the number of pounds by the height to which they are raised in a min ute, 150 X 220 gives 33,000 lb., and the power of a horse is generally expressed by a sum varying from 80,000 lb., to 36,000 lb., raised 1 foot high in a minute. Bolton and Watt express it by 32,0001b.; Woolf, by 86,000 lb. ; Tredgold, Palmer, and others, by 33,333 lb. One horse can draw horizontally as much as seven men.
In trains of machinery from to is allowed for friction in calculating its equivalent of horse power. equivalent Table of Power and Let us suppose 15 to represent the great est unloaded speed, and the square of 15, or 225, to represent the greatest load which can be sustained without moving ; the following table gives for each degree of speed, from 1 to 15, the corresponding load and useful effect :— Thus, if the greatest unloaded speed of a horse be 15 miles an hour, and the greatest weight he is capable of sustain ing, without moving, be divided into two hundred and twenty-five equal parts, his labor will be most advantageously em played if lie be loaded with 100 of those parts, and travel at the rate of five miles an hour. If he be thus employed it will
be found that he will carry a greater weight through a distance, in a given time, than under any circumstances.
A horse, upon a well-constructed rail road, can draw 10 tons at the rate of 2 miles per hour, or 5 tons 4miles per hour. The absolute force of the horse draw ing horizontally is, on average, 770 lb. From various calculations it would appear when the period of continuance is made an element in the calculation, that the power of a horse working eight hours a day is on an average not more than an equivalent to that of five men working 10 hours ; the most useful mode of ap plying a horse's power is in draught, and the worst is in carrying a load ; it has been found that three men carrying each 100 lb., will ascend a hill with greater ra pidity than one horse carrying 300 lb. The best disposition of the traces in draught is when they are perpendicular to the collar.
When a horse is employed in moving a machine in a circular path, the diame ter of this path should not be less than 25 or 30 feet ; 40 feet would be better than either.