- New Electro-Magnetic Engine. 135 
ble power in ordinary electro-magnetic machines, and occasion 
that singular anomaly,—that the actual power of such machines 
diminishes as their rate of revolution increases. Add to these 
difficulties, the influence of secondary currents, which, as I have 
shown several years since,* always remagnetizes a bar of iron 
after the battery current is cut off, and the third advantage of 
the new engine will be appreciated,—for in the first place, the 
secondary current occurs in all other forms of electro-magnetic 
machines, when the armatures or magnets are very near the 
point of greatest action, but in this engine the secondary current 
occurs at the farthest possible distance from this point; and 
_in the second place, the secondary current has no perceptible 
influence upon the inclosed bar when it does occur. ‘The me- 
chanical power derived from this arrangement, should it ever be 
found economical, will be increased, by increasing the number of 
small machines. Any length of stroke may be obtained by 
arranging the helices in a straight line and causing the bar or 
bars to pass through the whole length, multiplying the number 
of helices, in proportion to the length of stroke. 
It has long been a mooted question among mechanics, whether 
a rotary steam engine would have any real advantages over the 
reciprocating engine, and as no genius has arisen to give usa 
rotary engine which might claim comparison, it is séz// a ques- 
tion. But in regard to this kind of electro-magnetic engine, the 
rotary form is most desirable, for certain reasons to be hereafter 
explained. This interesting modification of the experiment, was 
matured some few days after the reciprocating engine was.com- 
pleted, and will be shortly explained. In addition to the power 
of the helix in drawing the bar within itself, I have availed my- 
self of an extra source of attraction, viz. the actual power of the 
magnet, which receives an additional impulse by the attraction 
between it and an armature or bar of soft iron. ‘This impulse, 
which is powerful, is received at an unfavorable moment, as it 
is nearly at the end of the stroke, when the crank is only a short 
distance from the dead point; but I have made use of it never- 
theless to advantage, by an arrangement which I will describe in 
the next number. In the rotary form there is no mechanical 
difficulty of this nature to overcome. 
* This Journal, 1838, Vol. xxx1v, p. 372. 
? ? Pp 
