May 17, 1888] 



NATURE 



59 



Sp. 12. Characteristics: with the expansion of the 

 continuous spectrum towards the blue, band 9 becomes 

 verv narrow, and cannot be observed with certainty. 

 The other bands, with the exception of 7 and 8, are 



becoming wider and paler, while 2 and 3 still gain in 

 supremacy. 



Sp. 13. Characteristics: 9 has now entirely disap- 

 peared, 2 and 3 still retaining their supremacy. 



I 2 3 



EC. FIRST SPECIES 



A LA5T , , 



5 6 7 8<> 9 



£ ORIGIN OF BANDS 

 5 OF THE BANDS. 



MEAN VALUES. 



.— Map showing the spectra of the various species of the bodies of Group II., and the probable origin of the bands. The carbon flutings are widest in 

 the first species, and gradually narrow until, in the last species, only a trace of 517 remains. The length of the continuous spectrum gradually 

 increases as the carbon flutings narrow. The carbon B 1 fluting, and the hydrocarbon fluting are only seen in species 8 to 12. 



Sp. 14. Characteristics : all the bands are pale and 

 narrow ; 2 and 3 will still be darkest, but the difference 

 will not be so great as in the species preceding. 



Sp. 15. Characteristics: in ordinary members of this 



group, 2 and 3 now alone remain visible : they are wide, 

 but feeble, as the continuous spectrum which has been 

 rapidly developing during the last changes is now 

 stronsr. 



