2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



fairly consistent. They lead us to expect that with more time for 

 preparation, and more numerous observations in 1948, very interest- 

 ing results may be obtained. 



As pictured in figure i, Publication 3843, the proposed prism 

 comprised a cemented combination of a 60° Jena U.V. Crown 3199 

 prism with an opposed Bausch & Lomb light flint L.F.3 prism of 

 22° refracting angle. We knew the dispersion characteristics of the 

 Jena glass prism from our holographic work on the solar constant, 



I" 



tV/lt^£ LENGTH , M/CROfiS 



Fig. I. 



-Curves of prismatic deviation, A, and wave length, and of dispersion 



dB 

 factor, -r-, B, and wave length. 



and we estimated those of the L.F.3 prism by comparison with glasses 

 listed on page 359, Smithsonian Physical Tables, 8th revised edition. 

 From these data the curves of figure 2, Publication 3843, were com- 

 puted. It proved impossible to procure Jena 3199 glass, and the 

 cemented combination finally prepared by Bausch & Lomb was a 60" 

 B. & L. B. S.C.I borosilicate crown with an opposed 23° B. & L. 

 L.F.3 ^ight flint prism. We were unable to determine its dispersion 

 through the desired range at Washington before the expedition, 

 though it was partially observed with great accuracy by Hoover and 

 Greeley. Hence at Mount Wilson we were unable to select knowingly 



