Polytechnic Association Proceedings. 975 



Two other important facts are also proved by what has becu 

 shown. First, that in 1658, when the needle pointed due north at 

 London, the magnetic pole was then situated on the meridian of 

 London, and between that and the North pole, and not on the 

 opposite side of the North pole, at one hundred and eighty degrees; 

 and secondly, that the revolution is from east to west. Because, 

 had the magnetic pole then been situated on the opposite side of 

 the North pole from London at one hundred and eighty degrees 

 (and it must have been on one or the other of these points), and 

 revolving in the ratio as we have seen, in order to produce a west- 

 erly variation at Greenwich or London, the revolution must have 

 been from west to east. And although in that case the variations 

 at London would have been precisely the same as they have been, 

 yet in passing over one hundred and eighteen degrees of longitude 

 it would place the magnetic pole to-day in longitude sixty-two 

 degrees west, where we know it is not, and the variations at New 

 York would have been at present easterly and increasing, instead 

 of westerly and increasing in that direction as we now know it is. 

 It is, therefore, certain that the revolution is from east to west. 



Having now gone so far, and as I believe demonstrated beyond 

 a doubt, the fact of the revolution of the magnetic pole, the subject 

 rises to a higher sphere, and the questions naturally suggested to 

 the mind are, what is polar magnetism, and what is the cause of 

 this revolution ? 



These are lofty questions, indeed, when we consider the source 

 and influence of the things we are to inquire about, and they are 

 only to be approached with caution and reverence. I will, how- 



all of which are perfectly consistent with, and corroborative of, the truth of my position. 

 He also says that in 1708 the variation of the compass in Massachusetts (probably at Cam- 

 bridge), was eight degrees west; in 1742, six degrees west, and in 1780, two degrees west. 

 This is not possible with the truth of my position, and one or the other must be in error. 

 If he had said east instead of west, it would have been in perfect accordance. It may be 

 an error of print, or the difference may have been caused by local attraction; but I am 

 more inclined to think that the difference arose from the fact that the observers in these 

 cases reversed the poles, and that their meaning was, that the variation of the true north 

 from the needle's point was so many degrees west. If we suppose this to have been the 

 case, and that the variations, as we now define variation, were east and not west, their 

 record would then be in perfect conformity with both the theory and progrees of revolu- 

 tion as we ha.ve explained it. Such a supposition is not improbable when we consider that 

 one hundred and sixty years ago the whole subject was but little understood or attended 

 to in this country; and when we reflect that from 1658 to the present time, the magnetic 

 pole has occupied two hundred and ten years in passing from the meridian of London to 

 it's present position, it could not have been in a situation to give a westerly variation at 

 Cambridge in 1708, and the foregoing solution of the Cambridge record is the only one 

 possible. 



