NATURAL PHILOSOPHY. 147 



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magnetic mass wliich some physicists have supposed to exist within the 



earth. 







The real cause of the magnetic polarity of the planets is, in my view, 

 the same for all, and Arago's experiment conducts to it in a straight line. 

 It results even from the condition of their existence. Each star, turning 

 around a central axis, and in determinate curves, is influenced by the mass 

 of these stars and their velocity at the circumference ; in a word, the 

 agent decomposing into two fluids, the normal magnetism of the earth and 

 the other planets is their rotation. A geometer examining this opinion, 

 would find, we believe, that the declination, inclination, and the perturba- 

 tions of the magnetic needle, are explained on this hypothesis much better 

 than on any other. 



Since my researches on circular electro-magnets, and in general on 

 bodies in rotation, I have sought much for experimental demonstration of 

 this theory, and have now the conviction that this is impossible, as it is 

 not possible for us, while upon the earth, to remove ourselves from the 

 action of its own magnetism. Whenever a development of magnetism 

 under the influence of rotation is observed, it is common to attribute it to 

 the inductive action of the earth, rendered so striking by the experiments 

 of Arago and Mr. Barlow. 



Alongside of the different sources of magnetism mentioned in Treatises 

 on Physics, friction, pressure, percussion, torsion, we should add rota- 

 tion, a mechanical action of equal title with the preceding, and whose 

 effects, produced through a sub-division, like that of magnetic polarity, 

 are found grouped at the extremities of the axis in rotation, in the same 

 manner as the poles develop at the extremities of a bar of iron when it is 

 subjected to torsion. 



NEW TELEGRAPHIC BATTERY. 



At a recent meeting of the Franklin Institute, Philadelphia, Dr. 

 Turnbull exhibited a new form of telegraph battery, devised by C. T. 

 Chester, Esq., of New York. Dr. T. remarked that this battery, while 

 it does away entirely with local action, employs the cheapest materials and 

 the most convenient arrangement of Darts. Its cells are lars;e, of strong 



O J. O ' fJ 



glass, and they are insulated from the shelves by a partial coating of elec- 

 trophorus. Its metals are amalgamated zinc, and a peculiar platinized 

 and peculiarly insulated plate, the result of much study and experiment. 

 The plates are supported by metal clamps and thoroughly insulated wood. 

 The construction is such as to secure perfectly against any cross-fire. 

 The plates can be removed and cleaned separately, without stopping the 

 working of the battery. The solution used to excite it is a dilute sul- 

 phuric acid. How free it is from local action, may be inferred from the 

 fact that it has been in constant use five months without being taken 

 down, and that the zincs last such an unprecedented time. The relative 

 cost of working the Grove, Darnell's, and the new battery, without taking 



