ELECTRO-MAGNETISM AS A MECHANICAL POWER. 535 
filled with mistrust on observing that this thought, which appeared to 
me so simple and natural, was not mentioned by any of the numerous 
natural philosophers who occupy themselves so assiduously with electro- 
magnetic experiments. I could not believe but that these notions must 
have struck them; but I was forced to suppose that they had either seen 
immediately the impracticability of them, or that, even if they had made 
some experiments upon the subject, they had met with insurmountable 
difficulties in its application. This long deterred me from making any 
experiments ; but in the lecture which I gave before this Society on the 
10th of December 1832, I could not refrain, when speaking of the 
powerful electro-magnets of Henry and Ten Eyck, from asking the 
question, “whether such a considerable power as that which is ob- 
tained by interrupting the electric current and then restoring it, could 
not be applied with advantage to mechanical science.” After that lec- 
ture I considered the subject again, and thought I had convinced myself 
of its practicability ; but that even if it were so, the result could not be 
very important, because the motion of the keeper must necessarily be 
very small. Notwithstanding, I had a more powerful electro-magnet 
made than any I had hitherto possessed, with which I intended to try 
the experiment ; and I regarded the expense the less, as this apparatus 
appeared to me at the same time to be very appropriate for the evolu- 
tion of the currents observed by Faraday ; for this purpose the arma- 
ture also must be covered with copper wire, and then each time the 
poles of the electro-magnet are reversed, a magneto-electrie current 
circulates through this wire. In the mean time I found another method 
whereby the object I had in view might be effected, and which would 
allow a greater degree of motion to the armature: I thought I could 
effect this in the following manner. I placed on the table two cylin- 
drical soft-iron horseshoes bound round with similar wires; so that when 
the electrical current was transmitted through both wires, the similar 
poles should lie opposite to each other: between these, and at a 
small distance from either, I placed a cylinder of soft iron, serving for a 
keeper; and then I expected to see the armature play to and fro between 
the two electro-magnets when I sent the electric current first round the 
one and then round the other electro-magnet. After several fruitless 
rough experiments it succeeded at last, and I therefore then instructed 
a turner to make an apparatus, that I might be able to repeat, by means 
of it, in a more easy and perfect manner, these yet very imperfect ex- 
periments. I had proceeded so far, when, on the 4th of January, I 
received the latest part of Baumgiartner’s Zeitschrift, published at 
Vienna on the 17th of November 1832. I there observed a treatise, 
intitled, “ Electro-magnetic Experiments of Salvatore Dal Negro, Pro- 
fessor of Natural Philosophy in the Imperial University at Padua,” 
(translated from the Italian). The author says in the Introduction : 
“ Philosophers have already known for some time the power of elec- 
