Chemistry and Physics. 425 
current excited by the vanishing of the magnetism, to which it is pro- 
portional. Whena second bar of soft iron is caused to approach the 
squares of the currents it is clearly necessary to distinguish between 
these two cases of attraction in contact and attraction at a distance. 
The author gives the following summary of his results: 
(1.) The attraction of U-shaped electro-magnets with an equal num- 
ber of windings of the electro-magnetic spirals is proportional to the 
squares of the magnetizing current force. 
(2.) The attraction o magnets is, with equal currents, proportion- 
al to the square of the number of windings of the magnetizing spirals. 
(3a.) The attraction of U magnets is proportional to the square of 
d U mag 
nets an agn 
multiplied by the square of the number of windings. 
rals of an equal number of windings closely surrounding the core, is 
accurately proportional to the square roots of the diameters of these 
cylinders. 
(5.) For the particular case in which the surface of contact does not 
disturb the result, the attraction and the sustaining force are, with equal 
magnetizing forces, proportional to the diameters of the bar or U mag- 
nets. 
(6.) The attraction of bar and U electro-magnets, with equal mag- 
netizing forces, increases the nearer the whole of the windings are to 
(7.) The attraction, like the sustaining force of U electro-magnets, 
ceteris paribus, remains the same whatever be the distance of the 
branches of the magnet. 
(8.) The length of the branches of a U electro-magnet has no influ- 
ence on its attractive or sustaining force if the windings of the spiral 
surround its whole length. 
In addition to these laws the author has found that the attraction 
which a helix or spiral exerts upon a soft iron bar placed in its axis 
lows the same law as an electro-magnet, so that we have 
(9.) The attraction of a spiral is proportional to the square of the 
magnetizing current multiplied by the square of the number of wind- 
ings. — Pogg. Ann., xc, 248, 436, Oct. and Nov., 1853. 
6. Identity of Niobium and Pelopium.—H. Rosé has communicated 
Continued researches have, however, completely established the fact 
that pelopic and tantalic acids are essentially different, while between 
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