1888.] 



of the various Species of Heavenly Bodies. 



57 



diminished, and the true absorption flutings of Mg, Fe, Mn, Pb, and 

 the band of Ba, should be enhanced in intensity. 



There will be an inversion between the radiation and absorption. 



The highest intensity of the absorption phenomena will be indicated 

 by the strengthening of the bands 2, 3, 4, 5, and 6, and the appear- 

 ance of the other flutings and bands specially recorded in a. Orionis. 

 The bands 7 and 8 will disappear as they are special to a low tempera- 

 ture, and will give way to the absorption of manganese, iron, b, &c. 



This inversion, to deal with it in its broadest aspect, should give us 

 at the beginning 7 strong, and 2, 3 weak, and at the end 7 and 8 weak, 

 and 2, 3 strong. 



The first stage, representing almost a cometic condition of the 

 swarm before condensation has begun, has been observed in JNTos. 3,* 

 23, 24, 25, 36, 68, 72, 81, 118, 247, 249. There is a very large number 

 of similar instances to be found in the observations. The above are 

 only given as examples. 



The last stage, before all the bands fade away entirely, has been 

 observed in Nos. 1, 2, 26, 32, 33, 38, 40, 61, 64, 69, 71, 75, 77, 82, 96, 

 101, 116. As before, these are only given as instances. 



It is natural that these extreme points along the line of evolution 

 represented in the bodies under consideration should form, as I think 

 they do, the two most contrasted distinctions recorded by Duner — 

 that is, recorded in the greatest number of cases. 



Origin of the Discontinuous Spectrum. 



I have already shown that when the meteorites are wide apart, 

 though not at their widest, and there is no very marked condensation, 

 the spectrum will extend farther into the blue, and therefore the 

 flutings in the blue will be quite bright ; in fact, under this condition 

 the chief light in this part of the spectrum, almost indeed the only 

 light, will come from the bright carbon. Under this same condition 

 the temperature of the meteorites will not be very high, there will 

 therefore be little continuous spectrum to be absorbed in the red and 

 yellow. Hence we shall have discontinuity from one end of the 

 spectrum to the other. This has also been recorded, and in fact it is 

 the condition which gives us almost the most beautiful examples of 

 the class (196, * Herculis, 141, 172, 229). 



The defect of continuous light in the blue in this class, after conden- 

 sation has commenced, and the carbon flutings are beginning to 

 disappear, arises from defect of radiation of the meteorites, and hence 

 in all fully- developed swarms the spectrum is not seen far into the 

 blue for the reason that the vapours round each meteorite are at a 

 temperature such that fluting absorption mainly takes place, although 



* The references are to the numbers of the stars in Duner's catalogue. 



