12 REPORT — 1891. 



A very great advance lias been made in our knowledge of the consti- 

 tution of the sun by the recent work at the Johns Hoi^kins University 

 by means of photography and concave gratings, in comparing the solar 

 spectrum, under great resolving power, directly with the spectra of 

 the terrestrial elements. Professor Rowland has shown that the lines 

 of thirty-six terrestrial elements at least are certainly present in the solai- 

 spectrum, while eight others are doubtful. Fifteen elements, including 

 nitrogen as it shows itself under an electric discharge in a vacuum tube, 

 have not been found in the solar spectrum. Some ten other elements, 

 inclusive of oxygen, have not yet been compared with the sun's spectrum. 



Rowland remai'ks that of the fifteen elements named as not found in 

 the sun, many are so classed because they have few strong lines, or none 

 at all, in the limit of the solar spectrum as compared by him with the arc. 

 Boron has only two strong lines. The lines of bismuth are compound 

 and too diffuse. Therefore even in the case of these fifteen elements 

 there is little evidence that they are really absent from the sun. 



It follows that if the whole earth were heated to the temperature of 

 the sun, its spectrum would resemble very closely the solar spectrum. 



Rowland has not found any lines common to several elements, and in 

 the case of some accidental coincidences, more accurate investigation 

 reveals some slight difference of wave-length or a common impurity. 

 Further, the relative strength of the lines in the solar spectrum is gene- 

 rally, with a few exceptions, the same as that in the electric arc, so that 

 Rowland considers that his experiments show ' very little evidence ' of 

 the breaking up of the terrestrial elements in the sun. 



Stas in a recent paper gives the final results of eleven years of research 

 on the chemical elements in a state of purity, and on the possibility of 

 decomposing them by the physical and chemical forces at our disposal. 

 His experiments on calcium, strontium, lithium, magnesium, silver, sodium 

 and thallium, show that these substances retain their individuality uiider 

 all conditions, and are unalterable by any forces that we can bring to bear 

 upon them. 



Professor Rowland looks to the solar lines which are unaccounted 

 for as a means of enabling him to discover such new terrestrial ele- 

 ments as still lurk in rare minerals and earths, by confronting their 

 spectra directly with that of the sun. He has already resolved yttrium 

 spectroscopically into three components, and actually into two. The 

 comparison of the results of this independent analytical method with the 

 remarkable but different conclusions to which M. Lecoq de Boisbaudran 

 and Mr: Crookes have been led respectively, from spectroscopic observa- 

 tion of these bodies when glowing under molecular bombardment in a 

 Tacuum tube, will be awaited with much interest. It is worthy of remark 

 that as our knowledge of the spectrum of hydrogen in its complete form 

 came to us from the stars, it is now from the sun that chemistry is pro- 

 bably i\\)< wt to be enriched by the discovery of new element?. 



