1889.] Variability in condensing Swarms of Meteorites. 401 



The relation of the present observations to former ones is shown 

 in the accompanying diagrams (figs. 1 and 2). 



[In each observation the six most widened lines in each region are 

 recorded, so that in each 100 observations there are 600 lines in each 

 region. The relative numbers of the lines which are due to iron, 

 nickel, titanium, and unknown substances are graphically represented 

 by the curves. The dotted line refers to the lines of iron, the chain 

 line to those of nickel, the multiple line to those of titanium, and the 

 thick continuous line to those of unknown substances. 



The minimum period occurred in 1879, and the maximum at the 

 end of 1883, so that the observations now nearly extend through a 

 Sun-spot cycle. 



It will be seen that the conclusion I arrived at in 1886,* namely, 

 that " as we pass from minimum to maximum, the lines of the chemical 

 elements gradually disappear from among those most widened, their 

 places being taken by lines of which we have at present no terrestrial 

 representatives," is supported by the continued observations, espe- 

 cially in the F — b region. 



The 150 observations now added were made by Messrs. Fowler and 

 Taylor, and reduced and mapped by Messrs. Coppen and Porter. — 

 November 1, 1889.] 



II. " On the Cause of Variability in Condensing Swarms of 

 Meteorites." By J. Norman Lockyer, F.R.S. Received 

 June 27th, 1889. 



I. The General Theory. 



One of the general conclusions I arrived at in my paper on 

 " Researches on the Spectra of Meteorites "f was as follows : — "Most 

 of the variable stars which have been observed belong to those classes 

 of bodies which I now suggest are uncondensed meteor- swarms, or 

 condensed stars in which a central more or less solid condensed mass 

 exists. In some of those having regular periods the variation would 

 seem to be partly due to swarms of meteorites moving round a bright 

 or dark body, the maximum light occurring at periastron." 



And again in 1888,^ referring to the former class, I added, "If 

 the views I have put forward are true, the objects now under 

 consideration are those in the heavens which are least condensed. 

 In this point, then, they differ essentially from all true stars like 

 the Sun. This fundamental difference of structure should be 



* ' Roy. Soc. Proc.,' vol. 40, p. 352. 

 t ' Roy. Soc. Proc..' vol. 43, p. 154. 

 t ' Rov. Soc. Proc.,' vol. 44, p. 81. 



2 e 2 



