130 Experinnnts and Ohfifvalians on the Magnttic ^erpent'tnt. 



tural fitualion, but all the pieces, when broken, to infinity, ftill exhibit two very dilliniTt 

 poles. Pieces of five inches cll.inicter aft on the needle at the diftance of half a foot. The 

 examination of the magnetic axes alTords an objeft of curious enquiry. They are moftly 

 ■found in a direction parallel to that of the foliated grain ; nevcrthelefs, [ have found fome 

 which crofs it perpendicularly. Fragments extremely fmall, of the magnitude of o.oi of a 

 cubic line, flicvv a very ftrong pol.irity in proportion to their mafles. You fee them turn 

 very fuddenly when the poles of the wea'teft magnet are fuccclFively prefentcd to them. It 

 is a very ftriking phenomenon, that a flone pofielTed of fo high a degree of polarity fhould 

 exhibit no attraftion for iron which is not magnetifed. I have never obfsrved the fmallelt 

 particle of filings of iron adhere to the fcrpentine ; but the ferpcntine, reduced to powder, 

 attaches itfelf very readily to the magnet. 



You will enquire with impatience, if it be well proved that my fcrpentine is not mixed 

 •with magnetic iron ; whether this mixture may not be fulTiciently intimate to enter into the 

 <ompofition of each particle of the rock.' I can allure you, that I have made the moit alli- 

 duous enquiries in this refpedt. All my experiments were made in conjun£lion with Mr. 

 Godeking, whofe knowledge and abilities are a fufiicient aflurance againft error; but we 

 were decidedly convinced, that if the magnetic force cannot adhere to the earthy fub- 

 flances which form the bafe of the fcrpentine, it can be attributed only to the oxide of 

 iron with which it is coloured. Thefe are our rcafons : The rock has no mixture of me- 

 tallic fubftances. It prefcnts only here and there a few fragments of talc or amianthus ; but 

 neither pyrites, nor fchoerl, nor o£lahedrons of magnetic iron. When reduced to very fine 

 powder, itrefemblcs pounded chalk. The microfcope difcovers only earthy parts, of a clear 

 whitifh green. The fpecific gravity of this fcrpentine is very fmall. 1 find it only from 

 1.901 to 2.04 alTuming water to be l.O. There are not confequently any minerals but 

 pumice-ftone, mountain-leather, and fome varieties of the opal, which do not equal our 

 fcrpentine in denfity. The chemical experiments we have hitherto made, prove that it con- 

 tains, like the jade or lapis ollaris, oxided iron; but not iron capable of attra£lion by the mag- 

 net. The fplutions in muriatic acid, mixed with the nitric acid, are yellow, and not green like 

 thofc which the micaceous iron, and all the ores which contain pure or metallic iron, afford. 



Here then is a very (Iriking phenomenon, namely, the polarity of fuper-oxigcnated iron. 

 We learn by the valuable experiments of my celebrated countrymen Klaproth and Wenzel, 

 that pure nickel and cobalt are attra£l:ed by the n.agnet; we know that iron flightly oxideJ 

 (the black oxide) is alfo affedled ; but how great the difference between this Hate of oxida- 

 tion, and that of the iron which colours the fcrpentine, various calcareous (tones, and 

 perhaps even certain vegetable matters! What difference between a fubllance which acSls 

 alike on the two extremities of the needle, and a Itone of which the fmallelt portions excr- 

 cife a fpontaneous polarity ! Let us purfue the path of obfervation ; let us coUedl indubi- 

 table facts. By this method the theories of natural philofophy will be ellabliflied on folij 

 and durable foundations. 



Ohfervntions on the Shiie ivUch luasforivarded to Sir JOSEPH BaNKS u'lth the preceding Jilemoir. 

 Dfscription. — IT is of a blucifli opake black colour, every where iiiterfperfed with mi- 

 nute particles of a yellowifli rather filky white, and of no regular figure. No appearance 

 of fymmctry or cryRallization prefents itfelf, except oa one fide, where a rough indication 



of 



