654 



RECORDS. 



Si 0„. 

 AI2O3 

 Fe,0, 



Molecular Ratio. 



.61.61 1.025 



.10.87 ' 106 



• 5-89 037 



Quantitative Ratio. 

 4.100 



.858 



FeO 73- 



CoO 18. 



MgO 27. 



Is O I4-43- 



NejO 3.02. 



010 



002 

 007 



153 



Mn O. 

 H^O.. 

 CaO ... 



.010 

 .041 

 .020 



.44 



. .74.. 

 . II5- 



99-74 



In interpreting the formula of Orthoclase from these results, 

 with reference to the normal ratio of the quantivalences, 



R : R : Si = I : 3 : 1 2 



it seems necessary to assume an isomorphous substitution of a 

 part of the heptads by the dyads, here found in unusual 

 excess. 



It also seems natural to connect this excess of protoxides with 

 the general incipient decomposition of the mineral, the minute 

 fractures throughout its material, possibly produced by expan- 

 sion through absorption of oxygen and water, its remarkably 

 low specific gravity, and perhaps the frequent cur\'ature of its 

 faces and cleavage-planes. 



Professor J. F. Kemp called attention to the unusual pres- 

 ence of cobalt-oxide in a feldspar, shown in the analysis. 



Doctor Hovey then gave a veiy interesting description, with 

 lantern illustrations, of the geological and mineralogical excur- 

 sions in Russia, held in connection with the recent International 

 Congress. Many of the lantern pictures were beautifully col- 

 ored ; they referred in part to ethnographic observations ; and 

 the accompan}-ing remarks a"\\akened much interest. 



Alexis A. Julien, 



Secretary. 



