Oct. 14, 1880] 



NATURE 



565 



From the similarity of the flame spectrum to that of the sun 

 in one case, and from the dissimilarity in the other, we may 

 imagine that in the former case— that of sodium— we are 

 dealing with a body easily broken up, while lithium and 

 potassiimi are more resistant ; in other words, in the case 

 of sodium, and dealing only with lines recognised generally 

 as sodium lines, the flame has done the work of dissocia- 

 tion as completely as the sun itself. Now it is easy to 

 test this point by the method now under consideration, for 

 if this be so then (i) the chief lines and flutings of 

 sodium should be seen in the flame itself, and (2) the 

 spark should pass through the vapour after complete 



volatilisation has been effected without any visible 

 effect. 



Observation and experiment have largely confirmed 

 these predictions. Using two prisms of 60° and a high- 

 power eyepiece to enfeeble the continuous spectrum of 

 the densest vapour pjodiiced at a high temperature, 

 the green lines, the flutings recorded by Roscoe and 

 Schuster, and another coarser system of flutings, so far 

 as 1 know not yet described, are beautifully seen. I say 

 largely, and not completely, because the double red line 

 and the lines in the blue have not yet been seen in the 

 flame, either with one, two, or four prisms of 60^, though 



-Position of Spectroscope tor discovering Vapours close to the Metal. 



the lines are seen durins, volatilisation if a spark be 

 passed through the flame. Subsequent inquiry may 

 perhaps show that this is due to the sharp boundary of 

 the heated region, and to the fact that the lines in question 

 represent the vibrations of molecular groupings more 

 complex than those which give us the yellow and green 

 lines. The visibility of the green lines, which are short, 

 in the flame, taken in connection with the fact that they 

 have been seen alone in a vacuum tube, is enough for 

 my present purpose. 



With regard to the second point, the passage from 

 the heat-level of the flame to that of the spark after 

 volatilisation is complete, produces no visible effect, indi- 

 cating that in all probability the effects heretofore ascribed 

 to quantity have been due to the presence of the mole- 

 cular groupings of greater complexity. The more there is 

 to dissociate, the more time is required to run through the 

 series, and the better the first stages are seen. 



J. Norman Lockyer 

 {.To be continued.) 



WILLIAM LASSELL, LL.D., F.R.S.'^ 



■npHE scientific world will receive with deep regret the 

 J- intelligence of the death of this distinguished astro- 

 nomer. The smaller circle of those who knew Mr. Lassell 

 personally will deplore the loss of a friend of rare worth. 

 Mr. Lassell passed away without suffering soon after five 



I Based on an obituary notice written by the present writer for the Times. 



o'clock on the morning of Tuesday, October 5, in the 

 eighty-second year of his age, full of years and greatly 

 honoured and respected. 



In the words of Sir John Herschel, Mr. Lassell "be- 

 longed to that class of observers who have created their 

 own instrumental means, who have felt their own wants 

 and supplied them in their own way." The qualities 

 which enabled Mr. Lassell to do all this made him what he 



