Editorial 



The December number of the Astrophysical Journal gives a 

 translation of a paper " On the Constitution of Gaseous Celestial 

 Bodies," by A. Ritter, which possesses much geological signifi- 

 cance if its general conclusions are trustworthy. The original 

 paper is one of a series of eighteen which appeared between 

 the years 1878 and 1883 in Wiedemann's Annalen, but its astro- 

 nomical and geological bearings appear to have escaped the 

 attention they merit, and for this reason it is now reproduced. 

 Ritter attempts to compute the time which would be occupied 

 by a gaseous solar sphere of the dimensions of the earth's orbit 

 in contracting to the dimensions of the present sun ; in other 

 words, the time of evolution of the solar system from the sepa- 

 ration of the earth to the present stage under the Laplacean 

 hypothesis, with certain qualifications. The computation is neces- 

 sarily based on certain assumptions, some of which require 

 modification in the light of more recent investigations, but any 

 competent attempt at a mathematical discussion of the rate of 

 solar evolution under the gaseous hypothesis constitutes a notable 

 contribution to the cosmical phases of geology. The conclusion 

 is reached that about 5,500,000 years ago the solar radius was 

 equal to the radius of the earth's orbit. On the assumption that 

 the effective radiating disk of the sphere was always equal to 

 the whole disk, Ritter concludes that the solar mass shrank from 

 dimensions of the earth's orbit to a dimension ten times the 

 present sun's diameter in the remarkably short period of 255,710 

 years. On the assumption that the effective radiating disk was 

 half of the whole disk, he finds that a similar shrinkage would 

 take 511,420 years. In the latter case the total time occupied 

 by the solar mass in contracting from the earth's orbit to its 

 present dimensions would be about 5,765,000 years. This con- 



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