Clarice and Schneider — Constitution of the Silicates. 405 



An attempt was made to take the atomic weight, but the 

 result obtained, 190, is probably too high, the color showing 

 that part of the sulphate was changed to a basic salt. This, 

 however, t with the color of the oxides, a reddish-brown, and the 

 fact that the solutions do not yield an absorption spectrum, 

 suggests that a chief portion of the earth is terbium oxide. 



The result of the analysis is as follows : 



Specific gravity = 4 18. 



Molec. 

 Ratio. 



Juantiv. 

 Itatio. 



CaO 

 MgO 

 FeO 



FeoOs 



[Yt, Er, Trj 2 3 



[Ce, La,Di]o0 3 



Nb,0, 



Ta 2 5 



TiO., 



Si0 2 



33-22 



0-74 



0-23 ) 



0-50 \ 



5-66 



5-42 



0-10 



4-38 



5-08 

 44-12 



0-08 



99-53 



56 



40 



•593 | 



•018 f 



Fe 3 4 



•611 or 23 x 2 1-22 1 — 4 



1-52 or 3 



160 

 428 

 328 

 268 

 444 

 82 

 60 



15} 



12 V 



•035 



•0 



•003 



•016 



•011 



•538 | 



•001 \ 



•050 or2 x -300 J =1 



•027 or 1 xlO 



•270 



= 1 



2-43 or 5 



539 or 20 x 4 2-156 



■ ■ i' 



In conclusion I would express my thanks to Professor Gooch 

 of the Kent Laboratory for the valuable advice and assistance 

 freely given by him during the course of the analysis. 



Kent Laboratory. Yale University, July, 1890. 



Aet. LIII. — Experiments ujpon the Constitution of the Nat- 

 ural Silicates ; by F. W. Claeke and E. A. Schneidee. 



[Continued from p. 312.] 

 4. The Chlorite group. 



In this interesting but very obscure group of minerals, three 

 species were examined. First, the dark-green, broadly foli- 

 ated, mica-like ripidolite from Westchester, Pennsylvania. 

 This mineral has been repeatedly analyzed, and our results 

 confirm the older data. Second, a dark-green, scaly-granular 

 prochlorite, found in excavating the water-works tunnel in 

 Third, leuchtenbergite from the Scliis- 

 Slatoust, Siberia. The last mineral was 

 Mr. A. Losch of St. Petersburg ; but it 

 unfortunately contained inclusions which render our work 

 upon it of little value. The prochlorite was examined micro- 

 scopically by Mr. Lindgren of the U. S. Geological Survey, 

 who found it to be quite homogeneous. Analyses as follows : 



Washington, D. C. 

 chimsk mine near 

 kindly sent us by 



