444 Mr. Barlow on the Magnetic Effect inducedin Iron [June^ 



examined, and his letter, and that of Mr. DoUond, read ; as also 

 such parts of a correspondence between the Foreiga Secretary 

 and M. Reynier, as appeared necessary. 



It was then resolved that it appears to your Committee that 

 M. Guinand has not answered in a satisfactory manner to the 

 inquiry put to him through M. Reynier, whether he will engage 

 to furnish the London artists at a reasonable price, with flint 

 glass fit for their purposes, inasmuch as he holds out no assur- 

 ance of a regular supply, and has actually but a very Hmited 

 quantity of his glass to dispose of, and that principally in discs 

 not exceeding four inches in diameter; and your Committee 

 conceive that no degree of excellence in individual specimens 

 ■would authorise them to recommend their purchase by the 

 Society, unless supported by such assurances of constant sup- 

 ply as would render it a matter of public interest. 



Davies Gilbert. 



J. F. W. Herschel. 

 AprilW, 1823. Wm. Pearson. 



Article VIII. 



1825, 



Abstracts of Papers in the Philosophical Transactions for 



on the peculiar Magnetic Effect induced in Iron, and on the 

 Magnetism manifested in other Metals, S^c. during the Act of 

 Rotation. By Messrs. Barlow, Christie, Babbage, and 

 Herschel. 



1 . On the temporary Magnetic Effect induced in Iron Bodies hij 

 Rotation. By Peter Barlow, Esq. FRS. (With a Plate.) 



Mr. Herschel, in a conversation with Mr. Barlow on subjects 

 connected with magnetism, had inquired what effect Mr. B. 

 thought might result, from giving to an iron ball a rapid rotation. 

 The subject, however, dropped, and did not again occur to the 

 author, until recalled to his mind by some speculative views 

 which he entertained as to the cause of the rotation of the earth's 

 magnetic poles, &c. Being urged to the inquiry by these views, 

 as well as by Mr. Herschel's query, and encouraged by the 

 circumstance that Mr. Christie had found a permanent change 

 in the magnetic state of an iron plate by a change of position 

 on its axis, Mr. Barlow resolved to put the idea to the test of 

 experiment, on a scale that should decide the question in the 

 first instance. He describes the method he pursued, and the 

 results he obtained, in the following terms : 



" As soon as I had determined upon the experiment, I found 

 an excellent opportunity of making the first trial, through the 

 kindness of Generals Cuppage and Millar, of the Royal Artillery, 



