-1859] WRITINGS OF JOSEPH HENRY. 349 



an ordinary loadstone or artificial magnet This magnetism 

 is of an unstable character however, and Is subjected to 

 variations in the intensity and in the direction of its polar 

 force. In like manner we may consider the earth as an im- 

 mense prime conductor negatively charged with electricity, 

 though its condition in this respect may— like that of its 

 magnetical state— be subject to local variations of intensity, 

 and perhaps to general as well as partial disturbance. 



It may be said that this merely removes the difficulty of the 

 origin of the electricity of the atmosphere to an uu-explained 

 cosmical condition of the earth ; but even this must be con- 

 sidered an important step in the progress of scientific inves- 

 tigation. The hypothesis of Peltier has since his death been 

 rendered still more probable by the labors of Sabine, Lloyd, 

 Lament, Bache, and others, in regard to certain perturba- 

 tions of the magnetism of the earth, which are clearly refer- 

 able to the sun and the moon. It must now be admitted 

 that magnetism is not confined to our earth, but is common 

 to other — and probably to all the bodies of our system ; and 

 from analogy we may also infer that electricity, a co- 

 ordinate principle, is also cosmical in its presence and 

 the extent of its operation. That the earth is neg- 

 atively electrified was proved by Volta at the close of the 

 last century. For this purpose he received the spray from 

 a cascade on the balls of a sensitive electroscope; the leaves 

 diverged with negative electricity. 



This experiment has been repeated in various parts of the 

 globe, and always with the same result. That it indicates 

 the negative condition of the earth is evident, when we re- 

 flect that the upper level from which the water falls must 

 be considered as the exterior of the charged globe, and hence 

 must be more intensely electrified than points nearer the 

 centre. Since the earth is (as a whole) a good conductor of 

 electricity, as shown by the operations of the telegraph, the 

 electrical tension of it cannot differ much in different parts, 

 and we are at present un-acquainted with any chemical, 

 thermal, or mechanical action on land of sufficient magni- 

 tude to produce this constant electrical state. We are there- 



