SPECTRA OP SOME OP THE BRIGHTER STARS. 677 
Page 
Pig. 4.—Negative holder used in enlarging spectra .684 
Pig. 5.—Comparison of the G region of the spectrum of a Orionis and the Sun . . . 702 
Plates.— 
26. —Spectra of a Herculis — « Cygni. 
27. —Spectra of a Cygni — a Andromedm. 
28. —Reduction of the spectrum of a Orionis. 
29. —Spectra of a Andromedse — Arcturus. 
30. —Spectra of Arcturus and the Sun. 
I. INTRODUCTION. 
In the Bakeiian Lecture for 1888^ I brought together the various observations of 
the spectra of stars, comets, and nebulte which had been made up to that time, and 
showed that the discussion suggested the hypothesis that all celestial bodies are, or 
have been, swarms of meteorites, and that the difference between them is one of 
condensation only. The new classification of the heavenly bodies according to their 
spectra, rendered necessary by this hypothesis, differed from previous ones inasmuch 
as the line of evolution followed, instead of locating the highest temperature at its 
commencement as demanded by Laplace’s hypothesis, placed it much later. Hence 
bodies of increasing temperature were demanded as well as bodies of decreasing 
temperature. 
These conclusions were necessarily based on observations made by others, for the 
reason that my own work up to that time had been chiefly directed to the Sun. 
So soon, however, as my solar work rendered it necessary to determine the Sun’s 
true place among the stars in regard to its temperature and physical conditions, 
arrangements were made both at Kensington and Westgate-on-Sea to photograph 
the spectra of stars and nebulse. 
The present communication gives an account of certain parts of this inquiry so far 
as they have been carried; it is based upon 443 photographs of 171 of the brighter 
stars. 
Having this new and accurate basis of induction, the objects have been to 
determine :— 
(1.) Whether the hypothesis founded on eye observations is also demanded by the 
photographs. 
(2.) In the affirmative case to discover and apply new tests of its validity, or 
otherwise. 
The results as yet obtained are not sufficient to permit a discussion of all points 
bearing upon the hypothesis, but since most of the crucial ones are covered by the 
photographs already obtained, it appears desirable that the publication of the work 
done during the last two years should be no longer delayed. 
* ‘ Roy. Soc. Proc.,’ vol. 44, p. I. 
