Polytechnic Association Proceedings. 985 



was ouly in relation to the variations of the compass as observed at 

 sea, and Its practical application in commerce and navigation. But 

 I perceive that I have risen to much higher themes, and perhaps 

 some- may say, meddled with things too high for me; but I am 

 unable to perceive that I have at any time gone beyond a just infer- 

 ence from the truths shown. 



The simplification of the vast speculative ideas of geologists and 

 others, which this examination has suggested to my mind — my 

 thorough conviction of their essential truth, and that the truths 

 here shown may be availed of for the increase of knowledge and 

 the improvement of science — are my reasons for making public my 

 reflections on these matters. I submit them to the fate which 

 future developments may award to their truth or falsity. 



At the conclusion of this paper the Chairman remarked, that the 

 view now advanced regarding the moving poles, was about the 

 same as that of the late Dr. Sherwood, of this city. Thirty years 

 ago he put forth the idea that the two magnetic poles of the 

 northern hemisphere revolved around the axis of the earth once in 

 about six hundred and sixty-six years. That the line of no varia- 

 tion is now moving westward, is well settled; but observations 

 prove that such lines undergo very complex alterations, and that 

 the magnetism of our globe is not permanent. This subject has 

 occupied the attention of physicists for many years, and the best 

 idea of what has been accomplished in this direction, may be 

 obtained by perusing the article on "Terrestrial Magnetism," in 

 Nichols' Cyclopedia of Physical Sciences* 



Prof. Vanderweyde took exception to the principal positions of 

 Mr. Parker, and said, there were complications involved in this 

 question which could not as yet be satisfactorily accounted for. 

 Thermo-electric currents, generated by the unequal heating of the 

 globe by the exposure of one-half of its surface to the direct rays 

 of the sun, are now supposed to be the cause of the magnetic poles; 

 but the magnetism of the earth seems to be influenced in some 

 degree by other causes. 



At a late hour the Association adjourned. 



♦ All notions having the conception of four poles as their basis hare been utterly discarded 

 by the physical investigations of the illustrious Gaus ; nor did Hansteen himself (who gave 

 to these poles periods of revolution) " imagine that the arduous question, as to the nature 

 of terrestrial magnetism, could be resolved by any scheme so artificial." — Nichols' Cyclo- 

 pedia, p. 556. 



