On the Place of the Poles of the Atmosphere. 331 



vest of more. But the history of this science in times past, points 

 to so many occasions when rational trains of observation were im- 

 peded by the gratuitous introduction of a magnetic or electric ele- 

 ment, and thought to be needless thereafter, that the author sup- 

 posed that it might be of some service to shew that there was no 

 probability in the present case, either from actual observation or 

 natural considerations, that such a force should be looked to for ex- 

 planation. 



1st, Of actual observation. The poles of any force should bear a 

 certain known relation to the equator thereof; and if we find the 

 magnetic equator coincident with that of the atmosphere, which may 

 be considered as marked out by the line of equatorial calms, we 

 might reasonably suppose a connection between their poles. But 

 we do not. The mean positions of these equators are very different 

 from each other, and are subject to such totally different movements 

 through the year, that we cannot legitimately expect any nearer 

 coincidence in their polar points. 



2d, Of natural considerations. Mechanical force may always 

 be taken as the cause, and not as the consequence, of the magnetic 

 or electric currents by which it is accompanied. Certainly in the 

 case of an electrical machine, the electric spark may be made to 

 produce mechanical energy, as shewn in knocking small light pith 

 balls about ; but how incomparably less is this force to that em- 

 ployed to turn the machine round in the first instance to produce 

 the electricity. 



Now, the atmosphere enveloping and rubbing over the world, may 

 be taken as a large electrical machine, and does produce electric and 

 magnetic forces ; but these, although startling enough when wit- 

 nessed by us, little pigmies of men, are of infinitely small moment 

 compared to the force required to keep the whole atmosphere in mo- 

 tion, and to overcome its friction and inertia. 



Again, with regard to the intensity of terrestrial magnetism, it is 

 found with one of Gauss's large bars for determining the horizontal 

 force, by being suspended by two wires separated in the direction of 

 its axis, that the whole magnetic force amounts to less than 100,000th 

 part of the weight of the bar, that is, the force or attraction of 

 gravity. 



Similar experiments might be adduced, to shew that when a body 

 is heated, though electrical currents may be produced, and may have 

 a certain mechanical power, that yet the quantity of this is almost 

 infinitely small compared to what might be produced by employing 

 the heat directly.* 



Hence, there can be no reasonable doubt, that the principal 

 movements of the atmosphere must be owing to mechanical and 



* For a detailed account of Lieutenant Maury's speculation, vide Edinburgh 

 New Philosophical Journal, vol. li., p. 271 to 292. 



