Intelligence and Miscellaneous Articles. 307 



through the gases and vapours which constitute the entire mass of 

 a comet. 



^ It is certain that the greater portion of the light transmitted by 

 comets comes from the interior of their mass, and that it has 

 traversed deep strata of gas or vapours ; it must have undergone 

 there the elective absorption proper to those vapours and to the 

 compounds which result from them. / It is therefore natural that 

 dark lines or bands should be produced, different from Fraunhofer's 

 lines, which are peculiar to the light of the sun. Thus, besides 

 the faint but complete spectrum of that light, produced by re- 

 flection from the external parts where the absorption is insensible, 

 another spectrum must be produced, coming from the deeper parts 

 and greatly modified by more powerful absorption. 



The limits of a mere Note do not permit me to enter into the 

 details of my numerous spectroscopic observations of the comet 

 b 1881 ; but I can affirm that they appear to confirm this view ; 

 that is to say, the phenomena do not seem to require the inter- 

 vention of a light due to the incandescence of the cometary matter. 

 Hence it would follow that the discontinuity of this spectrum 

 comes from the same cause which gives rise to wide dark bands in 

 the spectrum of the sun when he is near the horizon, or in the 

 spectra of the atmospheres of the planets, with the sole difference 

 that in the comets the phenomenon is exaggerated in consequence 

 of the enormous thickness of the absorbing strata, their richness 

 in chemical compounds, and the faintness of the light which they 

 reflect toward us. It would therefore be necessary, for the spectral 

 analysis of the comets, *to proceed as we do for that of those atmo- 

 spheres — that is to say, to fix our attention not so much upon 

 the bright bands as upon those which owe their darkness to 

 absorption. — Comptes Rendus de V Academic des Sciences, 5th Sep- 

 tember 1881, t. xciii. pp. 439, 440. 



ON THE MAGNETIC METALS. BY M. GAIFFE. 



With the view of seeking out the best conditions for the pre- 

 paration of magnets of cobalt and nickel, of which I have the 

 honour to submit some specimens to the Academy, 1 tried those 

 metals in different states. 



The samples which were used for the trials were obtained by 

 means of the electrochemical processes communicated to the 

 Academy by Mr. Adams and me on January 7, 1870, and July 15, 

 1878, by employing currents of suitable intensity for rendering 

 the metals very hard. 



After dividing the samples into bars of nearly equal dimensions, 

 I left some bars of each metal in the hard state; others were 

 annealed; and others were annealed and forged. All were after- 

 wards magnetized in the same manner, and the magnet ism 

 measured directly with the magnetometer. After thirty-six and 

 seventy-two hours of rest, it was measured again. 



