CARBONATES AND SILICATES. 



81 



20.75 /* From the present curves, which include more observations in 

 the same region, it will be noticed that his last observation was in the 

 midst of a reflection band, beyond which the reflecting power decreases 

 to a low value as it approaches the 20.75 /x, band. 



30% 



56789 



/ 



FIG. 65. Potassium uitrate (a); Enstatite. 



POTASSIUM NITRATE (KNO). 

 (Curve a, fig. 65.) 



This compound shows a sharp maximum at 7.15^. As was noticed 

 elsewhere, the great shift of this maximum, as compared with the band 

 formed in the transmission curve, is due entirely to the great difference 

 in the reflection on both sides of the transmission curve, which is given 

 without correction for reflection. 



ENSTATITE (MgSiOs). 

 (Curve b, fig. 65.) 



This mineral is a mass of fine crystals. The reflecting power is low ; 

 there is a small maximum at 9.1 /*. 



o: 



789/0 

 FIG. 66. Calcite (a) ; Magnesite. 



// 



CALCITE (CaCO). 

 (Curve a, fig. 66.) 



Reflection from a natural cleavage face of Iceland spar. The trans- 

 mission curve shows a wide complex band extending from 6 to 8/t. 

 6 c 



