Terrestrial Magnetism. 103 



the rapid passage of one of the elements through the air, but with 

 increased energy, for the element itself would enter into the com- 

 bination. Still I contend that light and heat, or one of them, is 

 the result of the combining of the fluids of either magnetism, elec- 

 tricity, or galvanism, without the aid of any other body. This is 

 shown by passing electricity through the exhausted receiver of 

 an air pump, when we have beautiful displays of light, and the 

 effect is the more striking, the more perfect the vacuum. 



If there are three simple elements such as I have here supposed, 

 two of which are the fluids on the poles of the loadstone ; then 

 let these three be so unequally diff"used over and in the earth, as 

 severally to predominate, one at or near the north pole, another at 

 the magnetic equator, and the third at the south pole ; each at- 

 tracting the others, but repelling itself; and we have an elucida- 

 tion of terrestrial magnetism. 



If one of the elements entering into the constitution of light," 

 but not necessary to heat, abounded in the arctic regions, so as to 

 predominate in all terrestrial forms to the exclusion of the ele- 

 ments constituting heat, and this element is identical with one of 

 the fluids on the poles of the loadstone, then it must follow, that 

 the poles of greatest cold would coincide with the magnetic poles, 

 and the isothermal lines have some accordance to the magnetic 

 intensities of different latitude. 



The frequent occurrence of the aurora borealis in the northern 

 regions would be explained on this hypothesis, from one of the 

 constituents of light predominating in the arctic circle ,• and the 

 reason of its affecting the needle be at once shown : so I think a 

 solution may be afforded, for the curious facts, that heat while it 

 imparts the magnetic virtue to soft iron, diminishes with its in- 

 crease the power of the loadstone, while a white heat entirely 

 destroys it, and a red heat reverses the poles. 



I admit that these views are merely hypothetical, but they are 

 part of a more extended theory, which runs its ramifications 

 through all the phenomena of nature, according with so many 

 facts, that I cannot regard it as merely visionary ; but I admit 

 that much deliberation and caution are requisite in advancing such 

 positions, lest we should disturb science with unfounded specula- 

 tions. 



