326 the president's address. 



within the masses of tenuous gas composing many of the prin- 

 cipal nebulse, — matter linked together by some powerful cause of 

 union and common interest, and slowly generating the worlds of 

 future ages. Although we are still only on the threshold of 

 research into the most distant regions of the universe, few can 

 realize the amount of positive knowledge obtained by the aid of 

 spectrum analysis and photography, in relation to the material 

 structure of the heavenly bodies ; but like all scientific investi- 

 gations of a technical character, the complete details of the 

 subject can only be understood after a careful and systematic 

 study of the special theories and methods of observation. I can 

 hardly expect that many of you will have time or inclination to 

 do this ; for the present, therefore, I think we may now leave 

 this novel section of astronomical research to the care of those 

 who are skilled in the use of the spectroscope, and who, by their 

 successful work, are known to be scientifically interested in the 

 important subject of the physics of astronomy. 



