IN THE MINERAL SERIES. 43 



other hand, as protoxide. A subsequent examination by Von Kobell 

 disclosed the presence of both oxides, as fully established by the later 

 analyses of Rammelsberg and others. These analyses, the correctness 

 of which it is impossible to doubt, do not lead however to any general 

 formula ; nor can any formula of a satisfactory character, in a mineralo- 

 gical point of view, be obtained from (hem. It will be as well to 

 quote their results before proceeding with our inquiry. A is Stromeyer's 

 analysis, as calculated by Von Kobell ; JS, that of Rammelsberg ; 

 O, "Wackernagel's j and D, Francke's — all of Elba specimens. E, is 

 an analysis by E. Tobler, of a specimen from Herbornseelbach in 

 Nassau. {Ann. GJiem. und. Fharm. xcix. p. 122. Also Rammelsberg's 

 Mineral' Chetnie, p. 740.) 



A. B. C. D. E. 



Silica 29.28 — 29.83 — 29.45 — 29.61 — 33.30 



Sesquioxide of Iron 23.00 — 22.55 — 25.78 — 21.09 — 22.57 



Protoxide of Iron 31.90 — 32,40 — 28.60 — 32.71 — 24.02 



■ Protoxide of Manganese. 1.43— 1.50— 0.94— 1.55— 6.78 



'Lime 13.78 — 12.44—15.49 — 14.47 — 11.68 



Alumina 0.61 — — — — .... 



Water 1.27— 1.60— .... — — 1.12 



101.27 100.32 100.25 99.43 99.47 



Rammelsberg deduces from the above, the following oxygen ratios, 

 and calculates, from these, the formulae given below — truly stating, 

 however, at the outset, " es geht hieraus das wahre Verhaltniss nicht 

 mit Sicherheit hervor." 



RO. R'^Qs. SiO^. 



.4 ... 11.33 — 6.90 — 15.21 ..= 4.9 : 3 : 6.6 = 9.8 : 6 : 13.2 



B ... 11.08— 6.76 — 15.49 .. =4.9 : 3 : 6.9 = 9.8 : 6 : 13.8 



G ... 11.01 — 7.74— 15.29 .. =4.2 : 3 : 5.9 = 8.4 : 6 : 11.8 



D ... 11.75 — 6.33— 15.37 .. = 5.6 : 3 : 7.3 = 11.2 : 6 : 14.6 



^ ... 10.19 — 6.77— 17.29 .. = 4.5 : 3 : 7.7= 9.0:6:15.4 



1 5 (2 RO, Si 0"-) + 2 (Fe^Qs, Si 0^). This requires the oxygen ratio, 



10 : 6 : 14. 



II 3 RO, 2 Fe^O^ + 6 (RO, Si 0-). This assumes the sesquioxide to play 



an electro-negative part, and requires the oxygen ratio 9 : 6 : 12. 



m 2 (2 RO, Si 0^) + Fe^O^, Si 0^. This requires the oxygen ratioj 



4:3:6. 



IV 9(2 RO, Si 0^) + 2(2 Fe^O^, 3 Si 0^). This exacts the oxygen ratio, 



18 : 12 : 30. 



Apart from this want of concordance, these formulae do not serve 

 to connect our mineral with other species of kindred character. In 



