JOURNAL 



OF 



NATURAL PHILOSOPHY, CHEMISTRY, 



AND 



THE ARTS. 



yvNE 1797. 



ARTICLE I. 



A LetUrfromM.d. Humboldt to M. PicteT, on the Magnetic Polarity of a Mountain 



of Serpentine *. 



At the beginning of the eighteenth century the attention of natural philofophers was 

 entirely fixed on the phenomena of magnetifm. The progrefs which has fince been made 

 m the theory of eledlricity, and the preponderance which chemiftry has acquired over all 

 the other branches of natural hiftory, have diminifhed the intereft with which enquiries 

 into the nature of the magnetic fluid ought to have been purfued. It is true that vour 

 celebrated countrymen MefTrs. de Saufl-ure and Prevot have given vigour to this purfuit by 

 dtfcoveries worthy of their fegacity : the firft, by inventing an inftrument capable of mea- 

 furmg the comparative intenfity of the magnetic forces in different regions of the globe ■ 

 and the other, by reducing the laws of polarity to the fimple laws of attraftion. But thefe' 

 d.fcovenes have not afforded inducement fufficient to lead philofophers into a path fo ho- 

 nourably explored. The moft valuable work on the origin of magnetic forces has been 

 negeaed together with the calculations of the ingenious Coulomb, and his experiments 

 with the balance of Torfion. 



Having traverfed with the compafs in my hand great part of the mountains of Europe. I 

 became convmced that declinations caufed by maflis of iron in beds or in veins are in- 

 finitely kfs frequent than na.uralifts affirm. The obfervations which MefFrs. de SaufTure 

 and rrembley have made on the fummit of Cramont f, appear to me the more curious, as 



* I received this communication in manufcript from the Right Hon. Sir Jofcph Banks, Bart P R S Ar 

 It u w„„en ,„ French, under the title of .■ Lettre quatrieme de M. de Hutnboldt a M. Piftet. fur'la Pol'a^ J 

 Magnet,que d une Montagne de Serpentine." The fame Uberal promoter of fcience has favoured me wt I 

 pccmcn of .h.s rock w„h penniff,™ ,0 make exper.m,..n,s upon it. A few obfervations on this fpecimen re 

 added at the end of thu memoir. • N. ' '"'" ^" 



t Voyage dans le, Alpes, T. I. p. jvj.-T. If. p. 343. 



Vol. I.— JuNU 1797. O 



