306 Dr Turner on the Composition of the Minerals 



ly botryoidal disposition, and its crystals are very small, but 

 possess a higher degree of lustre than the larger ones of the 

 hemi-prismatic species. The stratum immediately below it, 

 (mentioned as calcedony,) is a kind of the ironsinter of Wer- 

 ner ; it is very thin, and covers a rose-red variety of the 

 macrotypous lime-haloide of Mobs, which resembles very much 

 the red manganese from the mine Krieg and Frieden near 

 Freiberg. It is less compact, and full of fissures lined with 

 a greenish substance, where it approaches to the covering of 

 the brown ironsinter. A small fragment of the rock, a rather 

 compact claystone, containing some quartz, and called " petro- 

 sileai" in the ticket, is attached to the brown-spar. 



If we reflect on the remarkable degree of resemblance pre- 

 vailing among the two species, and those contained in the 

 genus gypsum-haloide of the system of Mohs, we cannot he- 

 sitate a single moment, to refer them likewise to that genus, 

 whatever may be the kind or manner of combination of their 

 constituent parts. Nay, the determinations of natural history 

 appear more independent, and deserving of greater attention, 

 by seeming to be at variance on certain points with the results 

 of other sciences, though we may always look forward with 

 perfect security, that the laws will ultimately be discovered, 

 according to which each apparent discrepancy may be ex- 

 plained. 



Art. XVIII. — On the Composition of the Minerals described 

 in the preceding Paper. By Edward Turner, M. D. 

 F. R. S. E., &c. Lecturer on Chemistry, and Fellow of the 

 Royal College of Physicians, Edinburgh. Communicated 

 by the Author. 



Being obliged, in the execution of the following analyses, to 

 operate on very small quantities of each substance, and as 

 in such cases a slight error has an important influence on the 

 result, I cannot presume to publish them as absolutely exact. 

 They maybe regarded, however, as good approximations, and 

 will be found, if I mistake not, to give a satisfactory view of 

 the composition of the two minerals described by Mr Haidin- 

 ger in the preceding paper. 



