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OBSERVATIONS. 



This fossil has been said, but erroneously, to have much 

 resemblance to iron sand, from which it may be easily 

 distinguished by the fracture, lustre, and inferior specific 

 gravity. 



PHYSICAL AND CHEMICAL CHARACTERS. 



Menacane is attractable by the magnet, but much more 

 weakly than iron sand, or magnetical iron ore; it is infusible 

 by the common blow-pipe, or heat of a porcelain furnace, 

 exposed in a coal crucible, but melts, when in contact with 

 a clay one; it also melts quickly to a black bead, before a 

 blow-pipe animated by pure air. The menae contents may 

 be easily extracted by digestion Avith acid of sugar. Kla- 

 proth and Lampadius, about the same time, have shewn, 

 that it consists of nearly equal parts menae and iron calces. 



GEOGNOSTIC OCCURRENCE. 



This fossil has hitherto been only found, accompanied 

 by fine quartz sand, in the bed of a rivulet, which washes 

 the valley of INIanachan, in Cormvall. The neighbouring 

 mountains belong to the primitive order, in Avhich, most 

 probably, the menacane formerly constituted a superficial 

 layer; but, by their decomposition, and consequent degra- 

 dation, 



