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MOTIVE POWER EMPLOYED

the above inclination of plane, the amount ofadhesive power, which the engine can spareto the load, above that required to propelitself forward, will be inversely as the sine ofthe angle of inclination, or as the height of theplane to its length.

The above will give the limits to which thenature of their action restricts the application ofthis kind of engines, and will shew upon whatinclination of road they can be used : this w ill ofcourse vary with the weight of the engine, andthe load which it has to overcome ; but, in everycase, making K = the weight of the engine.If the total resistance, arising either from thegravity of a certain elevation of plane, or fromthe friction of the carriages, or from both con-bined, do not exceed 3 K 5 , the adhesion of thewheels will be sufficient to enable the engine toeffect a progressive motion in all states of theweather without slipping.

The leading object of all machines, espe-cially of this kind, is to perform a definitequantity of work in a given time: to do thiswith the least expenditure of power, therewill be in every case a certain load com-pared with the weight of the engine, which,when used, will make the performance a max-imum : it will, however, be impossible to as-certain this, without a perfect knowledge of all