306 



Analyses of Books 



[Oct. 



146. By examining the errors in the last colnmn of (his table, and. comparing 

 them willi the amount of the observed inclinations, I cannot but think that it will 

 be imniedialely admitted that tlie former beiir too gre:it a proportion to the latter 

 to. allow us to consider the formula by which the computations were effected, as 

 exhibiting the true law of magnetic action applicable to this case. 



1 should hope that my intentions in pointing out these apparent anomalies in the 

 theory we have been examining will not be mistaken; I have no motive for so 

 doing but to give those who are desirous an opporluity of explaining them, if they 

 admit of explanation, and not with the desire of invidiously calling in question the 

 accuracy of the views of a philosopher of such acknowledged talents and perseve- 

 rance as M. Coulomb. 



147. It has been observed that, besides the experiment mentioned in Art. 141, 

 I had made sc7eral others in connexion with the same inquiry; which, however, 

 for certain reasons, 1 shall not publish in the present instance, but shall content 

 myself with proposing, by way of conclusion, the following queries: 



The direction of the needle being supposed due to the action of an infinitely 

 small but powerful terrestrial magnet, how are we to account for the following 

 facts, viz. 



1. The disturbance or oscillation of the compass needle during lightning, the 

 Aurora; Boreales, and other meteoric phenomena. 



2. The tixed polarity given to certain bars of soft iron in exposed situations. 

 Or we may put the question thus: — If certain iron bars become permanently mag- 

 netic by tlieircontiguity with the terrestrial magnet,* why is not this the case with 

 all bars of the same metal ? 



3. How can we explain the curious circumstance, recently discovered by Mori- 

 chini, relative to the magnetism of the violet ray ? 



4. How, again, are we to reconcile with the hypothesis of Coulomb, the remark- 

 able fact, lately published by Colonel Gibbs, respecting the magnetic iron ore of 

 Succasunny, viz. " That the ore in the upper part of the bed is magnetic, but that 

 raised frdm the bottom has no magnetism at first, but acquires it after it has been 

 some time exposed to the influence of the atmosphere?" — (See Thomson's Annals 

 of Philosophy^ No. 81. 



» To prove that common iron may remain very long in immediate contact with 

 the most powerful magnets, without becoming itself magnetic, I may state the fol- 

 lowing striking fact: — 



Early in the course of my experiments I had been favoured with the loan of a 

 strong horse shoe magnet, which would support 841bs. the lifter of which had been 

 in contact with it, in all probability, for 45 years, and yet had not acquired the 

 least sensible degree of magnetism. This instrument was made for Mr. Adams, 

 the celebrated teacher of, and author on, navigation, about the year 1774 ; and at 

 his death passed into the hands of SirJames Lake ; it vvas afterwards purchased by 

 the Rev. Mr. Warren, of Edmonton, and by him presented to Mr. Adams, of the 

 same place, the son of its first possessor, to whom I was indebted for the loan of 

 it, as well as for the above particulars relative to its date, &c. 



