136 INORGANIC EVOLUTION. [CHAP. 



a something connected with this doubling of the Milky Way which 

 produces the conditions which generate these bright-line stars. 



By the labours of Duner, Pickering, McClean and Campbell, we 

 are beginning to get very definite notions as to the distribution of the 

 various chemically different stars in relation to the Milky Way. As 

 I have already noticed, there can be no question as to the intimate 

 association of the bright-line stars with nebulae. We must next then 

 consider the nebulae from the point of view of chemical distribution, 

 but here we are somewhat in a difficulty. 



I have already stated that with regard to the general question of 

 the nebulae it is impossible to speak with certainty, because at present 

 there has not been sufficient time and there has not been a sufficient 

 number of observers at work to classify the thousands of " nebula? " 

 which we now know of into those which give us the gaseous spectrum 

 and those which are entirely different, apparently, in their constitution, 

 and only give us what is called a continuous spectrum. Still we can 

 go a little way in this direction by means of some figures which I have 

 noted. The point is to see whether there is any difference in the dis- 

 tribution of those nebulae which are undoubtedly masses of gas, which 

 give us the so-called nebulous spectrum, and those other nebulae about 

 which at present we know very little, which give us so-called continuous 

 spectra. It is clear that on this point undoubtedly, at some future 

 time, a great deal will be learned. The figures I give bring the results 

 up to the year 1894. If we take the region near the Milky Way, the 

 region bounded by 10 galactic latitude north and south, and consider 

 the planetary nebulae, we find that there are forty-two ; but if we deal 

 with those which are further than 10 from the Milky Way, that 

 number drops to five. If we take other nebulae, not necessarily 

 planetary but gaseous like planetary nebulae, inasmuch as they give us 

 a spectrum of bright lines, we find that there are twenty-two in or near 

 the Milky Way, and only six outside. If we take the so-called nebulae 

 known to have continuous spectra, which need not be nebulae at all 

 we only imagine them to be nebulae because they are sa far away that 

 we cannot get a really true account of them we find that the condi- 

 tions are absolutely reversed. There are only fourteen of them in the 

 plane of the Milky Way, but there are forty-three lying outside it ; so 

 that the percentage within 10- of the Milky Way comes out to be 

 eighty-four in the case of the planetary and the other nebulae which 

 give us bright lines, and in nebulae with continuous spectra only twenty- 

 five. Therefore we get an absolute identity of result with regard to 

 the bright-line stars and the other objects which give us bright-line 

 spectra. 



There is another class of bodies of extreme interest. In fact, to 



