1887.] 



on Light as an Analytic Agent. 



85 



was of course quite wet after the first explosion from the water 

 formed but the lithium lines were none the less strong. Indeed 

 after the tube had been very thoroughly washed out, the lithium 

 lines continued to be visible at each explosion, though less brightly 

 than at first A good deal of continuous spectrmn Accompanies th^ 

 !ww- ' iT * u ^^^^"l^^PPi^g of spectra of different orders, makes 

 observations difficult, so a screen of red glass was used to cut this off 

 when the lithium red line was under observation. In any case 

 however, close observation of the flashes is very trying, from the 

 suddenness with which the illumination appears, and thetriefness of 

 Its duration. At first we compared the lithium line given by the 

 flash of the exploding gases with that produced by the flame of a 

 small Bunsen burner m which a bead of fused lithium carbonate was 



«L. 'i i^^ Tf/'i,*^^^^^^ ^* ^^"^- ^^il^ t^e flame-line was 

 sharply defined the flash-lme had a different character, and was always 

 diffuse at the edges; so that it was not possible in this way to sub- 

 stantiate the minute difference of wave-length indicated by theory, 

 of thf two^ fl^sh-lme certainly seemed a little the more refrangible 



We then tried taking the explosion in a tube bent round so as to 



pnTnT Tfi '^'f' *^%*''^ P^"*^ ^^ *^^ *"^^ being parallel to 

 each other, and the glass ends side by side (Fig. 2). The axis of the 



so W r/fl^ 1 T\^^'' f °'^'^^' ""'^^ *^^* ^^ ^^^ ^^^b of the tube, 

 so that the flash m that limb was seen directly ; and by means of two 

 reflecting prisms (r,r) the light from the other limb was thrown into 

 tne slit, and the two images were seen simultaneously one above the 

 otlier. As the gas was ignited from one end of the tube, the flash 

 was seen receding m one limb, approaching in the other, so that the 

 displacement of the two lines would be doubled. Still we were 

 unable to substantiate any relative displacement of the lines on 

 account of their breadth and diffuse character. By washing out the 

 tube the bi-eadth of the lines was considerably reduced, but thev 

 remained diftuse at the edges, and baffled any observation sufficiently 

 accurate to establish a displacement. Certainly there appeared to be 



