1892.] Spectra of some of the Brighter Stars. 327 



larger dispersion it becomes necessary to deal with the presence or 

 absence of individual lines. 



In the first instance, the various stars of which the spectra have 

 been photographed at Kensington have been arranged in tnbles, 

 without reference to any of the existing classifications, and taking 

 into account the finer details. The basis on which the main tabular 

 divisions of the spectra are founded is the amount of continuous ab- 

 sorption at the blue end. This distinction was not possible in the 

 case of the eye observations. 



The stars included in the first table are characterised by the ab- 

 sence of any remarkable continuous absorption at the blue end, and by 

 the presence in their spectra of broad lines of hydrogen. These have 

 been further classified in four sub-divisions, depending on the presence 

 or absence of other lines. 



In the stars of the second table there is a considerable amount of 

 continuous absorption in the ultra-violet, and the spectra beyond K 

 are very difficult to photograph as compared with the stars of the 

 first table. In these stars the thickness of the hydrogen lines is about 

 the same as in the solar spectrum. These also are arranged in two 

 sub-divisions. 



In all the stars included in the third table there is a very con- 

 siderable amount of continuous absorption in the violet, extending 

 to about G, and it is a matter of great difficulty to photograph these 

 spectra, as most of the stars of this class are below the 3rd magnitude. 

 The hydrogen lines are very thin. One sub-division includes the 

 spectra which show flutings shading away towards the less re- 

 frangible end of the spectrum. The other comprises stars without 

 flutings in their spectra. The brightest star in this table, a Orionis, 

 is discussed in detail, the result tending to show that the tempera- 

 ture of the absorbing iron vapours is not much greater than that of 

 the oxy-hydrogen flame. 



The relations of the various sub-divisions to which reference has 

 been made are then traced. 



One important fact comes out very clearly, namely, that whether 

 we take the varying thicknesses of the hydrogen lines or of the lines 

 of other substances as the basis for the arrangement of the spectra, 

 it is not possible to place all the stars in one line of temperature. 

 Thus, there are stars in which the hydrogen lines are of the same 

 average thickness, while the remaining lines are almost entirely dif- 

 ferent. These spectra cannot, therefore, be placed in juxta-position, 

 and it is necessary to arrange the stars in two series. 



The next part of the paper consists of a discussion of the photo- 

 graphic results in relation to the meteoritic hypothesis. In the 

 Bakerian Lecture for 1888, I brought together the various observa- 

 tions of the spectra of stars, comets, and nebulae, and the discussion 



z 2 



