Intelligence and Miscellaneous Articles. 309 



hoff, Weber, Helmholtz, Maxwell, Stefan, &c. for the motion of 

 electricity in material conductors must be extended by adding to 

 the electrostatic potential and the action of induction a term ex- 

 pressing the electrodynamic action, and easily calculated when the 

 current in the volume-element that acts and is acted on is resolved 

 into three components at right angles to one another and their reci- 

 procal action calculated according to an electrodynamic law (Am- 

 pere's for instance). — Kaiserliche Akademie der Wissenschaften in 

 Wien, math.-natarw. Classe, Jan. 15, 1880, pp. 11-13. 



RESEARCHES ON THE RELATIVE INTENSITY OF THE SPECTRAL 

 LINES OF HYDROGEN AND NITROGEN IN REGARD TO THE CON- 

 STITUTION OF NEBULA. BY CH. FIEVEZ, ASSISTANT ASTRO- 

 NOMER AT THE ROYAL OBSERVATORY AT BRUSSELS. 



Huggins's observations* having shown that the spectrum of the 

 nebulae 37 HIV. Draconis, 73 HIV. Cygni, and some others con- 

 sisted of a few bright lines, one of which, brighter than the others, 

 coincides with a nitrogen-line, and another, finer, corresponds with 

 the line F of hydrogen, he was led to investigate whether the com- 

 plicated spectrum of nitrogen might not be simplified by extinction f . 



He remarked that, by causing the induction-spark to spring be- 

 tween platinum electrodes placed before the objective of a telescope, 

 only one line of nitrogen was visible in the spectroscope applied to 

 the ocular extremity. 



Afterwards, examining the spectrum of nitrogen with a spectro- 

 scope having a prism of 60°, and placing near the eye a neutral- 

 tint prism corrected for refraction and possessing equal absorptive 

 power for all parts of the spectrum, he saw that the two groups 

 of nitrogen-lines in the orange were nearly extinguished, while 

 the lines in the green were very bright. And on employing a 

 small direct-vision spectroscope, Huggins found it possible, by in- 

 creasing the distance between the instrument and the spark, to 

 obtain a position in which the double line in the green (Pliicker's 

 group IV.) J coincident with that of the nebula was alone visible. 

 The spectrum of the spark in nitrogen then resembled that of the 

 nebula. 



Huggins's researches do not appear to have been carried further 

 in this direction ; nevertheless he believes that, if the spectrum of 

 hydrogen were reduced in intensity, the line F, which corresponds 

 with that of the nebula, would alone remain visible after the line 

 C and the other more refrangible ones had become too faint to affect 

 the eye. 



The verification of this hypothesis is connected with a very im- 

 portant question, viz. " Do the lines of the spectrum of a nebula 

 represent the total light emitted by that body ? or are they merely 



* " On the Spectra of some of the Nebulae." Philosophical Transactions, 

 1864, p. 437. 



t Phil. Trans. 1868, p. 542. 



% " On the Spectra of Ignited Gases/' Phil. Trans. I860, plate HV 

 Phil. Mag. S. 5. Vol. 9. No. 56. April 1880. Z 



