32 The Ottawa Naturalist. [May 



If the spectroscope had done nothing else than this, it would 

 have established a far reaching and most important generaliza- 

 tion, and one which enables us to develop a uniform and homo- 

 geneous theory of cosmical evolution, impossible without this 

 knowledge. 



If we look up at the sky on one of these brilliantly clear 

 nights, we see stars scattered more or less irregularly over the 

 whole hemisphere visible to us. The number visible to the 

 unaided eye at one time is generally much overestimated, the 

 maximum number being about 3,000 instead of millions as I 

 have heard some people express. The great majority of these 

 objects, as well as thousands of times as many more rendered 

 visible by telescopic aid, are suns shining with their own intense 

 light and heat, many of them similar to our own sun, while 

 many are in earlier or later stages of development, and of larger 

 or smaller size. Besides the stars and the planets, of which 

 latter there are generally not more than two or three visible to 

 the eye at one time, close scrutiny, and knowing where to look, 

 will enable to detect a few objects which look like faint hazy 

 stars but which, when viewed by the telescope, present an 

 altogether different appearance, have a more or less extended, 

 misty, hazy, nebulous appearance generally without sharply 

 defined boundaries. These are what are called the nebulae, 

 and, though not so numerous as the stars, nevertheless number 

 many thousands throughout the sky. 



When analysed by the spectroscope some of them give a 

 continuous spectrum, indicating a source composed of luminous 

 solid matter probably in the form of dust or small particles. 

 Others, notably the Great Nebula in Andromeda, the largest in 

 the sky, give an absorption spectrum similar in some respects 

 to that of our sun, indicating a stellar origin of the light, and 

 showing that these bodies are possibly Galaxies or Universes 

 like our own situated at almost inconceivable distances. Many 

 of the nebulae, the Great Nebula in Orion, the most beautiful 

 in the sky, being a conspicuous example, give bright line or 

 emission spectra indicating the elements hvdrogen, helium and 

 a gas unknown on the earth which, for want of a better name, 

 we call nebulium. Considerable speculation has been indulged 

 in as to the nature of nebulium which is generally considered to 

 be a very simple form of matter. Only last month a paper 

 appeared' in the Monthly Notices of the Royal Astronomical 

 Societv by Dr. J. W. Nicholson which assumed the atom of 

 nebulium to be of the nature of a positive charge of electricity 

 surrounded by a revolving ring of negative ions three or more in 

 number. Calculating mathematically the wave lengths of the 

 lines given by such a system they were found to agree quite 



