ee 
108 Hlectro-Magnetism, as a Moving 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 from 
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-magneétism, wary 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 mee 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. 
First.—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 - 
asecond. Admitting that electricity, even in its lowest state of 
tension, passed at this rate, still the time required in giving a very 
e magnet its maximum charge, would be a perceptible item- 
Therefore a single impulse or discharge, as from a common electri¢ 
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 siti to produce mo- 
tion, must be dispensed with, if the introduction of repulsive 
