438 PHYSIOGRAPHY. CLASS n. 



lar composition upon which they depend. Filiform, 

 capillary, reticulated, and arborescent shapes, also 

 leaves or membranes. Sometimes the individuals 

 are still discernible, but frequently also they can be 

 no longer recognised. Surface drusy, striated, or 

 smooth. Massive : composition not observable, 

 fracture hackly. Plates, superficial coatings, rolled 

 masses. 



OBSERVATIONS. 



1. Although the division which has been introduced in 

 the present species into gold-yellow, 'brass-yellow, and greyish- 

 yellow Native Gold, seems with some slight modifications 

 to agree with the geological relations of its varieties ; it is 

 yet as little deserving of acceptance as any other division 

 within a natural-historical species. The gold-yellow va- 

 rieties comprise the specimens of the highest gold-yellow 

 colours, though there are some among them which have 

 a rather pale colour ; they include most of the crystals, 

 and of the imitative shapes, in fact the greater part of 

 the species itself. The brass-yellow native Gold is confined 

 to some of the regular and imitative shapes, of a pale co- 

 lour, which is generally called brass-yellow, and, as it is 

 said, of a less specific gravity than the preceding one ; but 

 this does not seem to have ever been ascertained by direct 

 experiment. The greyish-yellow native Gold occurs only 

 in those small fiat grains which are mixed with the native 

 Platina, and possess a yellow colour a little inclining to 

 grey ; they are said to have the greatest specific gravity of 

 them all. The real foundation of this distribution seems to 

 be the opinion that the first are the purest, the second 

 mixed with a little silver, and the third with platina. It 

 is not known whether the latter admixture really takes 

 place, but it is certain that several varieties of gold-yellow 

 native Gold contain an admixture of silver. Some mi- 

 neralogists unite the auriferous native Silver not improper- 

 ly with the present species. 



