ON PALLADIUM. UQ 



to be an ore coiififting entirely of the metals that were found 

 by Mr. Tennant in the black powder which is extricated by 

 Iblulion from the grains of platina, and which he has called 

 Iridium and Ofniium. But, fince the fpecific gravity of thete 

 grains lb much exceeds that of the powder, which by my ex- 

 periments has appeared to be, at the utmoft, ]4,2. I have 

 iftoiight it might deferve inquiry whether their chemical 

 compofi'-ion is in any refpe6l different. For this purpofe I 

 have feltcled a portion of them, and have requefted Mr. 

 Tennant >o imrier'akea comparative examination, from whofe 

 well known (kili in chemical inquiries, as well as peculiar 

 knowledge of the fubjetl, we have every reafon to expert 

 a complete anal^ fis of this ore. 



§ II. Hyacinths, 



Among thofe bodies which may be leparafed from the ore Very fmall liya- 

 of plalina, in confequence of their lefs fpecific gravity, by a *^'"^^ ^°""^, . 



. r r ■ ■, ,.•/-,,- ,, among the plati- 



turrent or water or ot air, there may be dilcerned a fmall t^a grains 3 



proportion of red ciyflals fo minute, that 100 of the largeft I 



could c()lle«5l weighed {Scarcely /^ of a grain. The quantity 



which I po(ie(s is confequently too fmall for chemical analyfis ; 



but their phyficai properties are fuch as correfpond in every 



re(pe6l with thole of the hyacinth. I was firft led to compare 



them With that ftone by their fpecific gravity, which I con- 



jeflured to be confiderable from their accompanying other 



Aibftances, that appear lo have been coileded together folely 



by reafon of their (uperior weight. 



Like the hyacinth, thefe cryftals lofe their colour imme- 

 diately and entirely when healed ; they alio agree with it in 

 their hardnels, which is barely futficient to fcratch quartz, but 

 is decidedly inferior to that of the topaz. 



The principal varieties of their form may be very well un- 

 derftood by defcription. 



]ft. In its moft (impie ftate the cryflal may be confidered VarlcMsof 

 as a rectangular prifm terminated by a quadrilateral obtufc '^^"" ^°'''"^» 

 pyramid, the fides of which fometiroes arife direct from the 

 fides of the prifm ; but, 



2dly. The pofition of the pyramid is generally fuch that its 

 fides arife from the angles of the prifm. In this cafe the tides 

 of the prifm are hexagons, 



3dly. It 



