% 



OBSERVATIONS. 



Of all fossils, this has the strongest resemblance to iron 

 sand ; into which, as Mr. Werner first observed, it actually 

 graduates, but may be distinguished from it by the shade 

 of brown in its colour; by its superior external, and inferior 

 internal lustre; by its less specific graA^ty; but, chiefly, by 

 being only slightly, and that- by apowerful magnet, attract- 

 ible. From nigrine and menacane, it differs sufficiently in 

 fracture and lustre. This, as well as nigrine, was first con- 

 sidered as a particular species by Werner; both which deter- 

 minations were afterwax'ds con^firmed by the analysis. 



CHI;MICAL. QHARACTEIIS. 



As in the foregoing species, the menac calx may here be 

 readily extra,cted by acid of sugai', the residuum being dis- 

 solved in ^qua regia: on the addition of tartarised tartarin, a 

 lemon yellow powder falls to the bottom, which is tartarised 

 menac; what remains in the solution is iron. Lampadius, 

 to whom Ave owe the analysis, found that menac and iron 

 ai'e here in a decreasing proportion; the latter amounting to 

 about 20 per cent. A late experiment has shewn him, that 

 iron sand contains the same principles, but, probably, in an 

 inverted proportion. 



GEOGNOSTIC 



