

of Magnetism by Rotation. 95 



Mr Barlow is not quite accurate in stating that the hypo- 

 thesis which I suggested was deduced from a comparison of 

 his results ; the fact having been precisely as I have stated in 

 your Number for June last. 



As Mr Barlow did not adopt the idea of a sphere circum- 

 scribing the needle itself, until after I had explained to him 

 my particular views of the subject, and as neither of us can 

 claim any originality when we indicate the relative situations 

 of two points by a radius, the angle which it makes with a 

 plane, and that which its projection on the plane makes with 

 a plane at right angles to this, I consider that the statement of 

 your correspondent, " Mr Christie, adopting the views of his 

 friend Mr Barlow,'" &c. is incorrect, and that therefore no 

 courtesy could authorise it. 



I know not whether, from what Mr Barlow has sard of his 

 having been in Edinburgh a short time before the publication 

 of the report of our experiments in your Journal, and of in- 

 formation being derived from him, we are to consider him as 

 the author of this report ; but if such be the fact, candour re- 

 quired that, in his " Illustrations of some Facts," &c. he 

 should distinctly avow it. For my own part, although I might 

 have recollected that Mr Barlow was in Edinburgh at this 

 time, I could not suppose that any statement, tending to in- 

 fluence the character of a report of the philosophical disco- 

 veries of others, as well as his own, could have been derived 

 from him. 



The explanation that Mr Barlow has given respecting the 

 detailed account of his experiments, which, without even the 

 slightest reference to their connection with mine, appeared 

 in the Edinburgh Philosophical Journal for July 1826, and 

 of the arrangement as to the time of our papers being present- 

 ed, renders a clear statement of facts necessary. 



When Mr Barlow, near the end of December 1824, or very 

 early in January 1825, informed me that he had discovered 

 some singular effects to be produced on a magnetised needle 

 by the rotation of an iron shell near it, and mentioned some of 

 them, I pointed out to him that these were simply a varia- 

 tion of the effects produced by the rotation of an iron plate, 

 which I had exhibited to him three years before, those effects 



