8o Anal-jft} if Sydney Earih.-^Artificial Magndt. 



Sir Jofepli Banks, the fame gentleman who had furnilhed Mr. Wedgwood with it, no 

 fufpicion can be entertained about its identity. 



Some of the esperiments which I have related, and which prove that fome of the finer 

 earthy pavticles remained fufpended in the concentrated muriatic acid, and were precipi- 

 tated when the acid was diluted with water, appear in fome meafure to account for the 

 miftake which has been made, in fuppofing that a primitive earth, before unknown, was 

 prefent ; but this alone will not account for many of the other properties mentioned by Mr. 

 Wedgwood : fuch as, 



lit. The repeated and excluGve folubility in the muriatic acid, and fubfequcnt precipi- 

 tation by water. 



2dly. The butyraceous mafs which was formed by evaporation. And 



3dly. The degree of fufibility of the precipitated earth. 



Thefe, indeed, I can by no means explain, but by fuppofing that the acids ufed by Mr. 

 Wedgwood were impure. This fuppofition appears to be corroborated by a palTage in Mr. 

 Wedgwood's paper, where he fays, " Here the Pruffian lixivium, in whatever quantity it 

 was added, occafioned no precipitation at all, (only the ufual blueiftinefs arifing from the 

 iron always found mthe common acids.'')* Now if (as it feems from this expreffion) Mr. 

 Wedgwood employed the common acids of the (hops, without having previoully examined 

 and purified them, all certainty of analyfis muft fall, as the impurity of fuch acids is well 

 known to every praftical chemiftf : but whether this was thecaufe, or not, of the effeSs 

 defcribed by Mr. Wedgwood, I do not hefitate to afTert, that the mineral which has been 

 examined does not contain any primitive earth, or fubflance poflefling the properties afcri- 

 bed to it, and confequently, that the Sydneian genus, in future, muft be omitted in the 

 mineral fyftem. 



VI. 



The Method of making Jlrong Artificial Magnets. By M. CouloMBX. 



1. SHALL here prefent the methods which I have found fuccefsful in conftru£ling artificial 

 magnets of very great force at a moderate expence. * * * * When a fteel rod or plate 

 is required to be rendered magnetic, and two bars are ufed for this purpofe, it is obvious 

 that it muft be of advantage to caufe the poles of thefe bars to act in conjunftion with 

 each other. This has given rife to the method of the double touch. Fig. i, Plate IV. 

 fhows the former practice of this method. If the bar n s be required to be impregnated, 

 the two bars SN, S'N', were placed vertically at the diftance of feven or eight lines from 



* Philofophical Tranfaftions, vol. Ixxx. partii. p. 313. 



+ It appears from Wedgwood's paper, that nearly one fifth part of the mineral was taken up by muriatic 

 acid, and that his folution was reckoned to have about fix grains of the foluble matter to three ounces of the acid. 

 From the experimental procefs of boiling, it feems probable that the aftual quantity of acid made ufc of, bore 

 an higher proportion to the matter taken up. If we admit the fuppofition of impurity in Wedgwood's acid, the 

 quantity of matter precipitable by water was probably lefs than two grains in the ounce : and after rejcfting the 

 Sydneian earth, as we undoubtedly muft, it may perhaps be an objeft worthy of enquiry to determine what 

 that fubftance was in which Wedgwood obferved the peculiar properties related in his paper. N. 



X Journal dc Pbyfique, xliii. 



each 



