74" On the Injliicnce of Heat on Magnetism, <§r. 



pears to me not improbable that all light, however attenuated, 

 and by what means soever elicited, is thus attended. 



Buxton, 21st May, 1823. J. MuRRAY. • 



MR. Murray's note on the influence of heat on mag- 



NETISBI, &C. 



Some interesting experiments made before the Royal So- 

 ciety of Edinburgh about the middle of last month, amply con- 

 firm the phaenomena which I have already described touching 

 the influence of heat in tlie deflection of the needle from the 

 magnetic plane. No question can now arise, and I feel grati- 

 fied in having been the first to elucidate and to excite attention 

 to the connexion obtaining between caloric and magnetism. 



In reference to the same subject, I quote with pleasure the 

 following from some judicious remai'ks on the magnetic needle 

 published at Genoa by the Baron de Zach. 



" Si mette una bussola fra due calamite, si lasciano cadere 

 i i"aggi del sole sulla calamita collocata all' est, 1' ago se ne al- 

 lontanera all' ouest quando sai'a scaldata la calamita. II con- 

 trario avra luogo, scaldando la calamita collocata all' ouest." 



The steel bar presented to me by Professor Morrichini 

 when at Rome, and which had been magnetized by the violet 

 ray of the spectrum, has since 1818 preserved its polarity, and 

 while I now write vibrates in the magnetic plane: it is however 

 not undeserving of remark here, that while its north pole is 

 attracted by the south pole of another needle, and repelled by 

 a north one, its soxith pole is indiscriminately attracted by 

 either pole of a needle, and would thus seem null. May we 

 anticipate the separation of the two poles, and their insulated 

 and independent exhibitions ? That time may come. 



It would appear from the excellent remarks of the Baron 

 de Zach already quoted from, that Governor Ellis has not been 

 the exclusi~oc observant of the influence of coW on the compass. 

 Perhaps the fact is to be found in the Transactions of the Royal 

 Society of London : but not having the records of that learned 

 body at this moment at hand, I quote again : " II capitano 

 inglese Middlcton traversando nel 1737 la bajo di Hudson, in 

 mezzo ad immensi ffhiacci oaleooianti, trovo die tutti gli a^hi 

 deile sue bussole aveano perduto il loro movimento, e che si 

 termavano indifi^erentamente in tutte le direzioni qualunque, 

 nelle quali si coliocavano col dito. Egli portu una di queste 

 bussole agghiacciate nel suo camerino, ma essa non riprese il 

 suo moto se non dopo averla messa vicino al fuoco, e dopo 

 averla ben riscaldata per un quarto d'ora : allora soltanto si 

 giro nella direzione magnetica. II capitano fu cosi obligato di 

 scaldare ogni mezz' ora tutte le sue bussole," &c. I am yours, &c. 

 Stranraer, N.B., 10 July 1823. J. MuRRAY. 



