342 FKAGMENTS OF SCIENCE. 



showed that the metals between which the spark passed 

 determined the bright bands in the spectrum of the 

 spark. Masson published a prize essay on these bands; 

 Van der Willigen, and more recently Pliicker, have 

 given us beautiful drawings of the spectra, obtained 

 from the discharge of Buhmkorffs coil. But none of 

 these distinguished men betrayed the least knowledge 

 of the connection between the bright bands of the 

 metals and the dark lines of the solar spectrum. The 

 man who came nearest to the philosophy of the subject 

 was Angstrom. In a paper translated from Poggen- 

 dorff s ' Annalen ' by myself, and published in the 

 * Philosophical Magazine ' for 1855, he indicates that 

 the rays which a body absorbs are precisely those which 

 it can emit when rendered luminous. In another place, 

 he speaks of one of his spectra giving the general im- 

 pression of a reversal of the solar spectrum. Foucault, 

 Stokes, and Thomson, have all been very close to the 

 discovery; and, for my own part, the examination of 

 the radiation and absorption of heat by gases and 

 vapours, some of the results of which I placed before 

 you at the commencement of this discourse, would 

 have led me in 1859 to the law on which all KirchhofFs 

 speculations are founded, had not an accident with- 

 drawn me from the investigation. But KirchhofFs 

 claims are unaffected by these circumstances. True, 

 much that I have referred to formed the necessary 

 basis of his discovery; so did the laws of Kepler fur- 

 nish to Newton the basis of the theory of gravitation. 

 But what Kirchhoff has done carries us far beyond all 

 that had before been accomplished. He has introduced 

 the order of law amid a vast assemblage of empirical 

 observations, and has ennobled our previous knowl- 

 edge by showing its relationship to some of the most 

 sublime of natural phenomena. 



