SPECTRUM OF THE GREAT NEBULA IN ORION. 91 
VI. General Conclusions. 
(1) The spectrum of the nebula of Orion is a compound one consisting of hydrogen 
lines, low temperature metallic lines and flutings, and high temperature lines. The 
mean temperature, however, is relatively low.* 
(2) The spectrum is different in different parts of the nebula. 
(3) The spectrum bears a striking resemblance to that of the planetary nebule and 
bright-line stars. 
(4) The suggestion, therefore, that these are bodies which must be closely 
associated in any valid scheme of classification is strengthened. 
(5) Many of the lines which appear bright in the spectrum of the nebula appear 
dark in the spectra of stars of Groups II. and IIL, and in the earlier stars of 
Group LV.; and a gradual change from bright to dark lines has been found. ~ 
(6) The view, therefore, that bright-line stars occupy an intermediate position 
between nebulz and stars of Group III. is greatly strengthened by these researches. 
I have to express my great obligations to Mr. Fowxer for the zeal and patience 
which he displayed in taking the photographs under somewhat unfavourable con- 
ditions. He is responsible for the determination of the wave-lengths of the lines and 
has assisted in the discussion. 
Messrs. BAXANDALL and SHACKLETON, computers to the Solar Physics Committee, 
have assisted in the preparation of the tables and the map illustrating the changes of 
spectrum with increasing condensation. 
* © Roy. Soc. Proc.,’ vol. 43, p. 152, 1887. 
