Homogeneous Bodies : with illtistrative Experiments. 23 



of other forms, they exhibit arrangements exceedingly similar 

 to each other when cast into cylinders, which are regularly 

 and uniformly cooled on every side ; and there is so little dif- 

 ference in the general aspect of a transverse fracture of the 

 two metals, that were it not for the difference of colour, it 

 would require some practice to distinguish the one from the 

 other. From this circumstance it appears highly probable, 

 that the same cause, whatever it may be, is the fountain of the 

 thermo-magnetism in both metals. 



85. It has been intimated to me by some very scientific 

 gentlemen, that impurities in the metal may possibly be the 

 cause of all the thermo-magnetic phaenomena which I have at- 

 tributed to homogeneous bodies ; and I must confess that for 

 some time I had entertained a similar opinion : experience 

 and observation, however, by no means sanction the conces- 

 sion. Some other cause than that of impurity in the metal 

 is unquestionably in active operation ; and to some other cause 

 we must direct our attention before we can accomplish an 

 explanation of the phaenomena in question. A very small 

 portion of tin added to bismuth, not only dispossesses it of its 

 magnificent crystalline ramifications, but also of the superla- 

 tive display of its natural innate thermo-magnetism : more- 

 over, that small morsel of tin not only paralyses the thermo- 

 magnetism natural to bismuth as a homogeneous metal, but 

 absolutely transfers its thermo-magnetic character as regards 

 other metals, from one extremity of the range to the other; 

 so that if pure bismuth be regarded as the most positive metal, 

 its alloy with tin will be the most negative substance, either 

 simple or compound, with which we are acquainted ; and 

 antimony, which has hitherto claimed the negative extremity 

 of the range, is highly positive to this simple alloy. 



86. The thermo-magnetism natural to antimony becomes 

 completely stagnated when mixed with tin or lead, and the 

 crystals of the metal become insignificant shapeless specks. 

 Zinc also, which when in larger masses displays its innate 

 thermo-magnetism in a degree sujierior to any other metal 

 except antimony and bismuth, becomes comparatively inert 

 by u mixture of tin or lead. 



And what perhaps may appear a more convincing fact than 

 all the rest is, that antimony and zinc, which separately, as 

 homogeneous bodies, display fine crystalline forms, and also 

 active thermo-magnetism, will, if mixed together as an alloy, 

 become robbed of both those distinguished cliaracters at once, 

 and the resulting metal appears as compact as the finest 

 steel. 



87. Wliatever may be the notions entertained as regartis 



the 



