Electro-Magnetic Machine. Sigs 
merely to try the principle, and this construction may be 
by a different and more efficient one. But with this arrangement, 
and notwithstanding the imperfection of the mechanism of the ma- 
chine—when the battery, requiring about one quart of diluted acid to 
immerse it, was attached, it lifted 16 Ibs. very rapidly, and when the 
weight was removed, it performed more than 600 revolutions per 
minute. 
So sensible was the machine to the magnetic power, that the im- 
mersion of the battery one inch into the acidulated water, was suffi- 
cient to give it rapid motion, which attained its maximum, when the 
battery was entirely immersed. It appeared to me that the machine 
had more energy with the electro-magnets, than with those that were 
permanent, for with the smallest battery, whose diameter was three 
inches and a half—its height five inches and a half, and the number 
of concentric cylinders three of copper and three of zinc, the instru- 
ment manifested as great power as it had done with the largest batte- 
ries, and even with a large calorimotor, when it was used with a per- 
manent instead of a galvanic magnet. With the small battery and 
with none but electro or galvanic magnets, it revolved with so much 
energy as to produce a brisk breeze, and powerfully to shake a large 
table on which the apparatus stood. 
Although the magnetization of both the stationary and revolving 
magnets was imparted by one and the same battery, the magnetic 
power was not immediately destroyed by breaking the connexion be- 
tween the battery and the stationary magnet ; for, when this was done, 
the machine still performed its revolutions with great, although di- 
minished energy ; in practice this might be important, as it would 
give time to make changes in the apparatus, without stopping the 
movement of the machine. 
It has been stated by Dr. Ritchie, in a late number* of the London 
and Edinb. Phil. Magazine, that electro-magnets do not attract at so 
great a distance as permanent ones, and therefore are not well adapt- 
ed for producing motion. On this point Mr. Davenport made the 
following experiment, of which 1 was not a witness, but to which I 
give full credit, as it was reported to me by Mr. Slade, in a letter 
dated New York, March 24, 1837. 
Mr. Davenport suspended a piece of soft iron with a long piece 
of twine, and brought one pole of a highly charged steel magnet 
* January, 1837. 
