368 PHYSICS. 



The same authors have published their investigations on the spectrum 

 of magnesium and magnesium-hydrogen previously observed by them. 

 {Nature J June, 1881, xxiv, 118.) 



Fievez has investigated the magnesium lines in the spectrum of the 

 sun, with a view to ascertain to what their variation is due. The con- 

 clusion is that the unequal reversal of the magnesium lines is caused by 

 a difference in the intensity of the lines themselves, and not by any 

 particular condition of the metal. (Aww. Chim. Phys., July, 1881, Y, 

 xxiii, 3G6.) 



Huntington has examined the spectrum of arsenic, using to produce 

 it a Pliicker tube, having one of its electrodes hollow and containing the 

 arsenic. The wave-lepgths were determined from Angstrom's scale by 

 comi)aring the lines with those of the sun, hydrogen, lithium, sodium, 

 thallium, and strontium spectra. Twenty-three lines were thus com- 

 pared, the bright and characteristic ones having wave-lengths of 6023, 

 6013, 5813, 5653, 5563, 5498, 5340 (the thallium line), 5103, 4623, and 4593. 

 {Am. J. ScL, September, 1881, V, xxii, 214.) 



Hartley has published a paper on the relation between the molecular 

 structure of carbon compounds and their absorption spectra. The evi- 

 dence obtnined is in favor of the view that the selective absorption ex- 

 hibited by aromatic compounds depends on the vibrations of the car- 

 bon atoms within the molecule, but that those atomic vibrations are 

 dependent upon the nature of the molecular vibrations themselves, and 

 are probably to be regarded as harmonics of these fundamental vibra- 

 tions. {J. Chem. Soc, April, 1881, xxxix, 153.) 



J. W. Draper has obtained what he calls a phosphorograph of the 

 solar spectrum, and has compared it with a photograph of the same 

 spectrum, as illustrating the antagonistic action of rays of higher as 

 compared with those of lower refrangibility. A photograph taken on 

 silver iodide,, in i^resence of a weak extraneous light, shows three re- 

 gions: (1) a blackened one extending from the boundary of the blue 

 and green to a little beyond the violet; (2) a region in the other direc- 

 tion to the inferior theoretical limit of the spectrum where the action of 

 the daylight has been altogether arrested; and (3) a similar protected 

 region beyond the violet. In a phosphorograph, taken on luminous 

 paint, there is annexed to the shining region a region of blackness, 

 broken below the red by a luminous lectangle arising from the coales- 

 cence of the bands a, /?, y, discovered by the author in 1842. If, now, 

 a gelatin sensitive plate be laid on the shining blue phosphorescent 

 surface, it is powerfully affected, and the constituent lines of the infra- 

 red bright rectangle are instantly recognized in the gelatin plate. The 

 paper deals also with the extinction of phosphorescence by red light 

 and with the infra-red bands in the sun-spectrum. (Am. J. ScL, March 

 1881, V, xxi, 171.) 



Coruu has studied the effect of atmospheric absorption upon the ultra- 



