i8o 



SELECTIVE REFLECTION BANDS. 



bands in the carbonates and in the sulphates is in agreement, at least as 

 a first approximation. Even with these data at hand, speculation in regard 

 to dynamical relations among atoms in the molecules had better be post- 

 poned until more data have been procured. 



160 



160 



140 



J 20 







' 100 



CD 



C 





 o 

 <J 



-t-> 



-C 

 CT) 



'co 



5 



80 



60 



40 



20 



4 5 6 7 8 9/0// 



Fig. io6. Maxima of reflection bands. 



/2 



/3/-i 



The data on the reflection bands of the carbonates at n to 15 p. is of 

 interest in connection with the question of the value of the extinction 

 coefficient necessary to give rise to selective reflection. In Carnegie Pub- 

 lication No. 65, page 70, is given the transmission band of a thin section 

 of calcite, from which it will be observed that the absorption band at 11.4 fi 

 coincides with the band found by reflection. It would seem desirable to 

 examine the transmission of thin sections of carbonates in this region of 

 the spectrum, using polarized energy, to compare with the intensity of 

 the bands found by reflection. The reflection bands at 14 /j. were fre- 

 quently found to be extremely weak, and in view of the importance of the 

 bearing of the results upon the whole subject, it seems highly desirable to 

 examine the transmission spectra of thin sections of these minerals (using 

 preferably polarized energy), to verify the aforesaid observations. (See 

 foot note on page 30.) 



