October 4, 1895.], 



SCIENCE. 



429 



laston, Fraunhofer and Fox Talbot had 

 worked at the subject long ago, it was not 

 till Kirchhoff and Bunsen set a seal on the 

 prior labors of Stokes, Angstrom and Balfour 

 Stewart that the spectra of terrestrial ele- 

 ments were mapped out and grouped; that 

 by its help new elements were discovered, 

 and that the idea was suggested that the va- 

 rious orders of spectra of the same ele- 

 ment are due to the existence of the 

 element in different molecular forms — allo- 

 tropic or otherwise — at different temper- 

 atures. 



But gi-eat as have been the advances of 

 terrestrial chemistry through its assistance, 

 the most stupendous advance which we owe 

 to the spectroscope lies in the celestial di- 

 rection. In the earlier part of this century, 

 whilst the sidereal universe was accessible 

 to investigators, many problems outside the 

 solar . system seemed to be unapproach- 

 able. 



At the third meeting of the Association, 

 at Cambridge, in 1833, Dr. Whewell said 

 that astronomy is not only the queen of 

 science, but the only perfect science, which 

 was "in so elevated a state of flourishing 

 maturity that all that remained was to de- 

 termine with the extreme of accuracy the 

 consequences of its rules by the profoundest 

 combinations of mathematics, the magni- 

 tude of its data by the minutest scrupulous- 

 ness of observation." 



But in the previous year, viz., 1832, Airy, 

 in his report to the Association on the prog- 

 ress of astronomj^j had pointed out that the 

 observations of the planet Uranus could 

 not be united in one elliptic orbit — a re- 

 mark which turned the attention of Adams 

 to the discovery of Neptune. In his repoi't 

 on the position of optical science in 1832, 

 Brewster suggested that with the assistance 

 of adequate instruments " it would be pos- 

 sible to study the action of the elements of 

 material bodies upon rays of artificial light, 

 and thereby to discover the analogies be- 



tween their aflBnities and those which pro- 

 duce the fixed lines in the spectra of the 

 stars, and thus to study the effects of the 

 combustions which light up the suns of 

 other systems." 



This idea has now been realized. All the 

 stars which shine brightly enough to im- 

 press an image of the spectrum upon a 

 photographic plate have been classified on 

 a chemical basis. The close connection be- 

 t^veen stars and nebulse has been demon- 

 strated ; and while on the one hand the 

 modern science of thermodynamics has 

 shown that the hypothesis of Kant and La- 

 place on stellar formation is no longer ten- 

 able, inquiry has indicated that the true 

 explanation of stellar evolution is to be 

 found in the gradual condensation of me- 

 teoritic particles, thus justifying the sug- 

 gestions put forward long ago by Lord 

 Kelvin and Prof. Tait. 



We now know that the spectra of many 

 of the terrestrial elements in the chromo- 

 sphere of the sun differ from those familiar 

 to us in our laboratories. We begin to glean 

 the fact that the chromospheric spectra are 

 similar to those indicated by the absorption 

 going on in the hottest stars, and I^ockyer 

 has not hesitated to affirm that these facts 

 would indicate that in those localities 

 we are in the presence of the actions of 

 temperatures sufficiently high to break up 

 our chemical elements into finer forms. 

 Other students of these phenomena may 

 not agree in this view, and possibly the dis. 

 crepancies may be due to default in our 

 terrestrial chemistry. Still, I would recall 

 to you that Dr. Carpenter, in his Presi- 

 dential Address at Brighton in 1872, almost 

 censured the speculations of Frankland and 

 Lockyer in 1868 for attributing a certain 

 bright line in the spectrum of solar promi- 

 nences (which was not identifiable with that 

 of any known terrestrial source of light) 

 to a hypothetical new substance which they 

 proposed to call ' helium,' because " it had 



