solid Hydrocarbons found in Petroleum Distillates. 99 



upper blue band 10*7, which is present in c and d. This was a 

 necessary result from Stokes's law, that fluorescent light never 

 contained rays of higher refrangibility than that by which it was 

 excited ; for the exciting light of b was only a little above F, 

 or 9 to 9*15 of the scale. 



Turpentine dissolves only a small portion of thallene, which, 

 however, communicates to it a blue fluorescence. When examined 

 in the manner just described, its appearance resembles in many 

 respects that of a similarly weak solution in benzole ; but there 

 are certain points of distinction. Thus the first band above F 

 is at some distance from it j the second band is decidedly double, 

 with its upper half of a paler colour ; and the band above G is 

 likewise evidently divided (see fig. 11). 



Fig: 1.1. 



The dark blades of absorption are not seen in this or in a 

 dilute benzole solution. 



A solution of thallene in carbon-bisulphide having, as we 

 have seen, its absorption-bands very low in the spectrum, pro- 

 duces also in this last method of examination a very characteristic 

 appearance. 



The first trail of light is entirely below F, and is pierced by a 

 dark blade; its colour is bright green. The next is midway be- 

 tween F and G, is bright blue, but does not penetrate very far 

 into the solution, and does not show a black blade. The upper 



