200 



F. W. Clarke — The Chlorite Group. 



Epichlorite, from the Hartz, by Rammelsberg. 

 Strigovite, Striegau, by Websky. 

 Epiphanite, Wermland, by Igelstrom. 

 The reduced analyses are as follows : 





Stilpnomel 



ane. 



Melanolite. 





Found. 



Calc. 



Found. 



Calc. 



SiO„ 



42-85 



41-80 



3425 



33-46 



Fe 2 3 



24-74 



26-01 



29-32 



29-74 



FeO 



23-69 



23-41 



26-48 



26-76 



H 2 



8-72 



8-78 



995 



10-04 





100-00 



100-00 



100-00 



100-00 





Epichlorite. 



Strigovite. 





Found. 



Calc. 



Found. 



Calc. 



Si0 2 



43-94 



45-50 



29-51 



30-20- 



Al 2 O s 



17-75 



16-58 



24-78 



24-25 



FeO 











36-05 



36-24 



MgO 



27-38 



28-17 











H 2 



10-93 



9-75 



9-66 



9-31 



100-00 100-00 100-00 100-00 



For epiphanite Igelstrom's analysis needs no reduction, if 

 we calculate with a ratio of Mg : Fe* ',7 : 5. 



Found. Calc. 



37-66 

 21-34 

 18-83 

 14-64 

 7-53 



Si0 2 



37-10 



Al 2 O s 



21-13 



FeO 



20-00 



MgO 



14-03 



H 2 



7-83 



100-09 



100-00 



The agreements are sufficiently close to establish the validity 

 of the hypothesis upon which the calculatious rest, although 

 they are not as good in all cases as might be desired. Still, 

 the formulae offered bring some order out of chaos, and are 

 therefore entitled to consideration until something better is 

 proposed. 



As between Tschermak's theory and mine, both represent- 

 ing the known facts fairly well, experimental research must be 

 the final arbiter. Until experiment has given grounds for de- 

 cision either theory may properly be used as a guide. Mine is 

 offered as a possible simplification of the problem ;- but both 

 may be supplanted by something more general still. Neither 

 theory exhausts all the possibilities of the question, and neither 

 can claim to be much more than a step forward in the series of 

 approximations by which the truth may be at last attained 



Washington, Dec. 12, 1891. 



