108 Elecfj^o-Magnetism, as a Movi?ig Power. 



and springs, and subsidence of battery action, which are easily 

 demonstrated to be remediable. It is not to be presumed that in 

 the present age, or perhaps ever, we shall arrive at a power iVom 

 electro-magnetism, which shall supplant the steam-engine, in its 

 grander operations. Indeed, it is not essential that this should be 

 the case, to render the invention even invaluable. Incalculable 

 benefit would be conferred upon society, if a new and simple me- 

 chanical power could be procured, available from that of a single 

 man to one or two horses. A multitude of mechanical operations 

 are now carried on by animal or water power, for which a low steam 

 power cannot well be used, from the fact that steam-engines below 

 one horse power, are hardly worth the making, and are troublesome 

 and expensive. A very natural question here arises ; if one horse 

 power can be obtained by electro-magnetism, why cannot two 

 horse, or any extent of power, be made ? Theoretically consid- 

 ered, it can be ; and electro-magnetic powers can only be limited 

 by the means used. But practically we have already been taught, 

 that (unlike other powers, where the largest engines are the most 

 simple and least expensive) electro-magnetic engines above a cer- 

 tain limit, increase in complication and expense in a much greater 

 ratio than the power obtained. To ascertain this limit, the pre- 

 cise point where economy ceases, is now the great, and ought to 

 be the only object of research. 



- ' There seems to be little doubt, from the data we already pos- 

 sess, that a power equivalent to one horse may be obtained with 

 economy. Before proceeding to point out the obstacles in the 

 way of the application of this power, the following general rules 

 are offered as deduced from actual experiment. 



pirst. — Whatever be the rate of passage of the galvanic cur- 

 rent, the full magnetization of a bar of iron requires time in pro- 

 portion to its hardness and size. Mr. Wheatstone has calculated 

 the rate of electro-motion, in good conductors, to be 188,000 miles 

 a second. Admitting that electricity, even in its lowest state of 

 tension, passed at this rate, still the time required in giving a very 

 large magnet its maximum charge, would be a perceptible item. 

 Therefore a single impulse or discharge, as from a common electric 

 battery, (be the quantity ever so great,) scarcely magnetizes. The 

 necessary consequences of this law are, first, small magnets an- 

 swer better than large ; second, change of poles, to produce mo- 

 tion, must be dispensed with, if the introduction of repulsive 



