Oh the Force of Magnetism. 377 



pursued his inv'estigation under many disadvantages ; but it is 

 much more remarkable that a literary man, who has written a 

 great deal, and who has probably read a little, should have 

 been so completely uninformed. 



If the author of the paper published in these selections had 

 been ignorant of the fact, he could never have remarked, in 

 the 11th section, that " a horizontal bar of soft iron will lose its 

 effect on the needle in four positions, at right angles to each 

 otlier; and a bar so inclined as to become perpendicular to 

 the dipping needle in the plane of the meridian, will lose its 

 effect in two opposite positions in that plane only ;" nor could 

 he have obtained the result now so strikingly verified by 

 Captain Sabine, if he had been so ignorant of the theory as 

 the Reviewer's assertion implies. 



It is true, that, if the account of Captain Flinders's obser- 

 vations is correct, the table given in this paper is not appli- 

 cable to such a ship as Captain Flinders's, in the neighbour- 

 hood of the equator, nor in the southern hemisphere ; and that 

 if the effect which was simply called regular in the first unpub- 

 lished impression of the paper, had been considered by the sea- 

 men intrusted with it for trial, as the principal or only effect, 

 though the author distinctly pointed out another effect, as fre- 

 quently occurring, under the name of the irregular attraction, 

 they might have been misled by the incautious application of the 

 table to all cases indiscriminately. 



It is also true, that Mr. Barlow and Mr. Lecount have as- 

 certained, that cast iron is capable of producing more distinct 

 effects, by its induced magnetism, than might have been ex- 

 pected by those who understood the term of soft iron, as syno- 

 nymous with conducting, in too literal a sense : and if Mr. 

 Barlow had claimed this as a discovery, and if he had also 

 claimed the merit of having first experimentally ascertained 

 the truth of his very ingenious friend Charles Bonnycastle's 

 theoretical assertion, that the induced magnetism of a shell 

 ought to be equal to that of a solid sphere ; it would have be- 

 come the duty of those, wiio sat in judgment upon his papers, 

 to examine how far these discoveires were actually altogether 



