1889.] of the various Species of Heavenly Bodies. 217 



11. The presence of hydrogen in the atmosphere of the hottest 

 stars ; 



III. The presence of carbon in stars on cooling ; 



IV. The decreasing densities of planets and satellites outwards. 



I hope shortly to be able to communicate the result of some experi- 

 mental work, which is now going on, which may throw light upon 

 this subject.] 



[Note added January 14, 1889. Since the above was written, I 

 have come across some observations of Comet C, 1886, made by 

 Mr. Sherman* on May 26th and 28th and Jane 4th. The perihelion 

 passage of the comet occurred on June 6th, so that all the observa- 

 tions were made near perihelion, when the comet was pretty hot. 

 Unfortunately, the individual observations are not recorded, and we 

 are therefore unable to trace the sequence of spectra. Seven loci of 

 light were observed, and four more were strongly suspected. The 

 wave-lengths given are 618'4, 600'6, 567'6, 5537, 545'4 (suspected), 

 535-0 (suspected), 517'1, 468'3, 433*2, 412'9 (suspected), and 378'6 

 (suspected). 



My suggestion as to the origin of this spectrum is that it was the 

 integration of hot carbon and hydrocarbon (431) radiation, cool 

 carbon absorption, manganese absorption, and lead absorption ; i.e., it 

 was similar to Coggia's Comet on June 13th (see p. 176), with the 

 addition of lead (546). The maximum at 618'4 was in all probability 

 the iron fluting, and that at 567*6 was probably the second fluting of 

 lead (568). This leaves the loci at 60O6, 535 '0, 412'9, and 378*6 

 unexplained, the latter three being only suspected.] 



II. "ON SOME EFFECTS PRODUCED BT THE FALL OF 

 METEORITES ON THE EARTH." 



PART I. FALLING DUST. 



In my paper of November 17, 1887, I stated that Professor Newton 

 and others have calculated that not less than twenty millions of 

 meteorites, each large enough to present us with the phenomenon of 

 a shooting star visible to the naked eye, enter our atmosphere daily. 

 If this be conceded, the upper parts of our atmosphere must be con- 

 stantly charged with meteoric dust, whether oxidised or not, in a 

 state of suspension, while it is possible that the earth encounters 

 particles finer than those which produce the phenomena of falling 

 stars. 



The only means open to us of determining the presence or absence 



* Amcr. Journ. Sci.,' vol. 32. 



