ON STATICS.

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force is something greater, but it cannot support the labour of more than 8hours a day, when drawing with a force of 200 pounds, or of 6 hours whenwith a force of 240, walking two utiles and a half an hour. It is generallysupposed, that in drawing up a steep ascent a horse is only equivalent to 3 or4 men, and the employment of horses in walking wheels, where the actionis similar to that of ascending a hill, has for this reason been condemned.For men,on the contrary, an ascent of any kind appears to aftord a favouraolemode of exertion. But, perhaps, the weight of the carriage, and of the horseitself, lias not always been sufficiently considered in the comparison. 'Iliestrength of a mule is equal to that of three or four men. The expense otkeeping a horse is in general about twice or three times as great as the hire ota day labourer ; so that the force of horses may be reckoned about half as ex-pensive as that of men. The horse Childers is said, although, perhaps, with-out sufficient, authority, to have run an English mile in a single minute; hisvelocity must in this ease have been 88 feet in a second, which would havebeen sufficient to carry him on an inclined plane without friction, or in avery long sling, to the perpendicular height of 120 feet.

A large windmill, on which Mr. Coulomb made many experiments, wascapable, on an average, of working eight hours a day; its whole performancewas equivalent to our estimate of the daily labour of 34 men ; 23 square feetof the sails doing the work of one labourer. The expense of the machinery,with its repairs, would probably amount to less than half the expense of anumber of horses capable of exerting the same force. \\ here a stream otWater can be procured, its force is generally more convenient, because moreregular, than that of the wind.

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A steam engine of the best construction, with a thirty inch cylinder hasthe force of 40 horses ; and, since it acts without intermission, will performthe work of 120 horses, or of 600 men, each square inch of the piston beingnearly equivalent to a labourer. According to Mr. Boulton, the consumption°f a bushel, or 84 pounds of coals, will raise 48000 cubic feet of water 10 feethigh, which is equivalent to the daily labour of 8 | men, or perhaps more:the value of this quantity of coals is seldom more than that of the work of aSln gle labourer for a day; but the expense of the machinery generallyAnders a steam engine somewhat more than half as expensive as the numberof horses for which it is substituted. According to other accounts, a 24 inch