44 Experiments on. Platina. 



. fliow themfehts more ftronglv the more widely the light is 

 difpeiTed over the body of the fan. 



t'ofteritv, perhaps, will be able to deduce the caufe of the 

 northern lights and other phaenomena from thcfe fuggeftions 

 refpeiliing the prodnftion of the luminous matter, and to 

 anfwer the important queftion — "■ By what circulation is 

 tliat noble matter, which din'ufes light and heat throughout 

 all nature, again conve^'ed back to infinite fpace; or whether 

 deftined and employed for the formation and maintenance 

 of organic bodies ?" 



VIII. Experiments on Platina. By L. Proust*. 



I. Of the foreign Bodies mixed with native or crude Platina. 



X HE bodies generally mixed with platina are fiony and 

 metallic fand, pvrites, gold, and mercury. The firft kind 

 of land confifts of fmall rock crylhds and frasrments of a hya- 

 cinth colour; the fecond conlifts of ferruginous fand of two 

 forts : the one oftaedral, and fufccptible of being attracted 

 bv the magnet, among which there are fome that do not 

 poflefs that property till after being heated : the other fort is 

 equally black and angular; but the angles are deftroyed in fuch 

 a manner, that it is not poflible to determine their figure, 

 which fcems to announce that they are not fo hard as the 

 preccdinsf. The latter are not fufceptible of being attrafted 

 by the nTacnet, even after they are heated, and when analyfcd 

 they exhibit new fubllances combined with iron ; phaeno- 

 mena bv which we are authorized to confider them in their 

 union as a mineralization of a peculiar kind^ as will be feen 

 hereafter. 



II. On the Method of feparating the ^and from the native 



or crude Platina. 



Place three or four pounds of crude platina on a large 

 table the edses of which are fomcwhat raifed, and at the 

 diilance of "a foot from one of the fides ; then fpread it out, 

 by means of a card or a rule, in fuch a manner as to occupy 

 the fpace of about two feet, and blow upon it obliquely with 

 a pair of hand bellows, to make the fand, which is always 

 lighter than the gold or platina, pafs to the oppofite fide. 

 It^this operation be" repeated five or fix times, taking care to 



• From Anr.iks ite Hifioria Natural, Madrid 1799, No. i. 



blow 



