VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 507 



rarefied dust, like a froth or scum ; but continuing it in the focus, it melted, 

 and ran into a yellowish glass, in which might be distinguished some particles 

 of metal like silver. I exposed some precipitate per se upon charcoal : it fumed 

 very much; and as it melted, one might see little globules of mercury unite, 

 and form themselves together upon the coal; but they dispersed again presently 

 in vapours. 



These experiments seem to prove, that there is in quicksilver, a sulphur which 

 may be separated by a very gentle heat, such as that of digestion : That as 

 soon as this sulphur is taken away, it loses its fluidity and brightness: That the 

 basis of mercury is a calx, or red earth: That this calx does not melt into glass 

 as the calx of other metals, because it is too volatile; and as soon as it melts, 

 is evaporated by the heat: That on restoring a sulphur to this calx, by exposing 

 it again upon charcoal to the focus, it immediately reassumes its metallic bright- 

 ness and fluidity, and becomes quicksilver. 



I know not yet whether this light earth, which remains on the stone after 

 the evaporation of the calx of the mercury, be a part of the earth of the mer- 

 cury, more exactly deprived of its oil, and consequently more fixed and proper 

 for vitrification; or whether it may not be some matter foreign to the mercury, 

 that fixes itself, and remains behind at its evaporation. 



The result of all these experiments is, that these four metals, which we call 

 imperfect, viz. iron, copper, tin, and lead, are composed of a sulphur or oily 

 substance, and of a metallic earth capable of vitrification: That from this 

 sulphur proceeds the opacity, brightness, and malleability of a metal : That 

 this metallic sulphur does not appear at all different from the oil of vegetables 

 or of animals: That it is the same in mercury, as in the four imperfect metals : 

 That these four metals have for their basis, an earth susceptible of vitrification : 

 That this earth is different in every one of these four metals ; as it vitrifies 

 differently in each of them. And that on this difference in vitrifying depends 

 the difference of metals. [Modern chemists consider metals as simple sub- 

 stances, and their calces, as compounds.] 



Observations on Incisions of the Cornea. By Mom. Gandolphe^ M. D. at Durkirk. 



N° 322, p. 387. 



Contusions on the bodies of animals do not always make the greatest im- 

 pressions on the parts that immediately receive them : I had an instance of this 

 lately, in a blow upon the eye. There was a slight contusion on the outside of 

 the part, with very little alteration to appearance ; but a vessel, being broken 

 within, poured forth a considerable quantity of blood: the eye also lost its 



3 T 2 



