:>28 Mr Filon, On the variation with the wave-length 



mo 



4500 



Fig. 4. Glass 192. 



fOOU 



5500 



6000 



Wave-lengths in tenth-metres. 



x Observations A.\ 

 + „ B, 



O » c 



® .. D 



ffi „ E 



6S"00 



iTable V. 



