444 Proceedinys. 



means of that iustrument in the hands of skilful observers. In a paper published in the 

 Nineteenth Century for February, Mr. Norman Lockyer presents us with a portion of the 

 results of the last ten years' work in this branch of science. From the one hundred 

 thousand observations recorded by him, he deduces the wonderful fact, that the fixed 

 stars may be roughly divided into four classes, distinguished by their (presumed) difference 

 in temperature. He shows that the brightest and hottest of the stars have a spectrum, 

 " marvellously simple," indicating in the main only two substances, hydrogen and calcium, 

 with faint traces of magnesium, and perhaps of sodium. Stars of the second-class are 

 neither so bright nor, it is believed, so hot. In this class our own sun is included, though 

 even his temperature is spoken of by Mr. Lockyer as so great as to be " beyond all 

 definition.' Stars of this class give a spectrum in which the indications of hydrogen are 

 distinctly enfeebled ; the evidences of the existence of calcium are increased in intensity, 

 as are also the indications of sodium and magnesium ; while the simple character of the 

 spectrum of the fu-st -class has been replaced by a combination of lines of "terrible com- 

 plexity." In speaking of the other two classes of suns, I will quote Mr. Lockyer's own 

 words: — "The complexity which we meet with in passing from the first-class to the 

 second, is one brought about by the addition of the lines produced by bodies of chemical 

 substances of moderate atomic weight. The additional complexity observed when we pass 

 from the second to the third, is brought about by the addition of lines due in the main to 

 bodies of higher atomic weight, and — this is a point of the highest importance — at the 

 third stage," that is, in the third-class of suns, " the hj'drogen, which existed in such 

 abundance in stars of the first-class, has now entirely disappeared. In the last class of 

 stars to which I have referred, the fourth, the lines have given place to fluted bands, at 

 the same time that the light and colour of the stars indicate that we have almost reached 

 the state of extinction." Mr. Lockyer puts the same facts in simpler form, thus — 



1. The hottest stars show lines of . .H + Ca -i- Mg 



2. The sun H -f Ca -f Mg -f Na + Fe 



3. The cooler stars Mg 4 Na + Fe + Bi -f Hg 



4. The coolest ; fluted bands of metals and metalloids. 



In the cooler stars the elements are found in a state of greater combination, while in 

 the hottest they are dissociated by the intense heat, so that the older (and therefore cooler) 

 a star has become, the less of free hydrogen will appear. On the earth the process of 

 cooling has reached the stage in which hydrogen is no longer found in a free state. All 

 that is here stated from Mr. Lockyer's paper, though extremely interesting in the connec- 

 tion in which I have introduced it, occurs in the original as part of the reasoning which 

 leads to the conclusion that many of the substances which have hitherto been regarded as 

 elementary are probably compounds, capable of dissociation at the transcendental tempera- 

 tures which exist in the hotter kinds of stars. Thus a general law is indicated which 

 may be expressed in these words : — The lowering of temperature in a mass of matter is 

 accompanied by a gradiially increasing complexity of chemical forms : and, of course, the 

 converse holds good that the higher the temperatnre the more completely ivill the elements 

 lohich form the chemical compounds he dissociated. 



Before passing from this subject, it will not be out of place to express the opinion 

 that we have here one of the greatest discoveries of these days, and one which opens out 

 a new field of investigation to which it is not easy to assign a limit. 



I had intended to call your attention to the remarkable progress which has lately 

 been made in other branches of science and in the application of science to the 

 comfort and convenience of man, but time will not permit more than a passing 



