138 



MENACANE, AND ITS ORES. 



.CHEMICAL CHARACTERS. 



ract^/ ' As in the foregoing species, the menac calx may here be 

 ■ readily extracted by acid of sugar, the residuum being dis- 

 solvedin aqua regia: on the addition oftartarised tartarin, a 

 lemon yellow powder fails to the bottom, which is tartarised 

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

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

 arc 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 OCCURRENCE. 



Geognostic Hitherto this fossil has been only found in the higli Riesen 



Qccurrence of mountains, which separate Silesia from Bohemia, near the 

 origin of the Iser, dispersed through the granitic sand which 

 forms the bed of that river. To what order of rocks it 

 owes its origin is uncertain; but its near affinity to iron 

 sand, which is exclusively an inmate of the flbtz trap forma- 

 tion, and the certainty, that this formation was formerly 

 superstratified, at a great elevation, on the Riesen mountains, 

 (as the remains, which form the Buchberg*, and occupy 

 the Schneegruben, sufficiently testily.) .render it highly 

 probable, that this fossil, also, may belong to that forma- 

 tion ; and, consequently, dates its origin from a much more 

 recent period than the foregoing species of this genus f . 



GENERAL REMARKS. 



General re- These are the Only fossils of this genus, with whose cha- 



xnarks on me- & ? 



* The Buchberg (which I enjoyed the invaluable opportunity of 

 ejcamining with my excellent and ever to be regretted friend) is the 

 highest basalt hill in Germany, being 2921 feet above the level of'thc 

 sea, and the highest basalt, except that small quantity lodged in the 

 cavity of the Schneegruben, which is some hundred' fett higher. I'he 

 hill itself is elevated about 500 feet above the Iser, that washes its gra- 

 nitic basis, and the Iserine is found at some distance below. We could, 

 indeed, discover no trace of it in the basalt of the present hill. — R. J. 

 ■ f Mr.Gregor (as stated in Nicholson's Journal) has found, that me- 

 nac is one of the constituent ingredients of basalt; a fact, which adds 

 much to the plausibility of Dr. Mitchell's very ingenious supposition. 



-R.J. 



racters 



