8 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ever, to the opinion that the connection between the variation 

 of mean temperature and the appearance of the solar spots 

 is indirect rather than direct, and that each results from some 

 general change in the solar energy. 12 A, March 30,434. 



PROOF OF THE NEBULAR HYPOTHESIS BY THE SPECTROSCOPE. 



Iii the September number of the American Journal of Sci- 

 ence, Professor Daniel Kirkwood presents the testimony of the 

 spectroscope in regard to the truth of the nebular hypothesis, 

 beginning by calling attention to the supposed annihilation 

 of this hypothesis by the observations of Lord Rosse and of 

 Professor Bond, both of whom succeeded, in March, 1846, as 

 they thought, in resolving certain supposed nebulae in the 

 stars. These observations were considered by the majority 

 of astronomers as fatal to the claims of the nebular hypothe- 

 sis. But, according to Professor Kirkwood, this has more 

 than recovered from the shock it received, and the more re- 

 cent application of the spectroscope to the investigation of 

 the nebulae proves its truth conclusively. The general result 

 of the later examinations he sums up in the following man- 

 ner: 



1. The ring nebula in Lyra, the dumb-bell nebula, the great 

 nebula in Orion, and others which might be named, are not, 

 as was but recently believed, extremely remote sidereal clus- 

 ters, but their light undoubtedly emanates from matter in a 

 gaseous form. 



2. According to Lord Rosse and Professor Bond, the bright- 

 er parts near the trapezium (in the nebula of Orion) consist 

 of clustering stars. If this be the true appearance of the 

 nebula under great telescopic power, then these discrete 

 points of light must indicate separate and probably denser 

 portions of the gas, and the whole nebula is to be regarded 

 rather as a system of gaseous bodies than as an unbroken va- 

 porous mass. 



3. Progressive changes in the physical condition of certain 

 nebulae are clearly indicated by the fact that nuclei have been 

 established which, as shown by their spectra, are not wholly 

 gaseous, but have passed, at least partially, to the solid or 

 liquid form. 



4. The spectroscopical analysis of the light of several comets 

 reveals a constitution similar to that of the gaseous nebulas. 



