272 PHYSICS. 



of lines by measurable amouuts — one or two seconds. — {Nature, xxi, 

 108, December, 1879.) 



Kundt has observ^ed the phenomenon of anomalous dispersion in 

 sodium vapor. In preparing to reverse the sodium line for a lecture 

 experiment, he perceived that when the sodium vapor was very dense 

 and the dark line very broad a peculiar bend outward appeared at the 

 ends and on opposite sides of the line. The cone of sodium vapor in 

 the Buusen flame acts as a jirism with its refracting edge horizontal 

 and turned u[)ward. If glowing sodium vapor give dispersion, this 

 cone should give, with horizontal rays passing through it, a vertical 

 spectrum, and if the rays have also passed through a glass prism with 

 a horizontal refracting angle, a spectrum of the form above described 

 should be obtained. From the position the refractive index of the 

 vapor is greatest for those rays which arc most deflected downward. 

 The refractive index increases as the band is approached from the red 

 side, is less on the green side, and then rapidly increases again. — {N'atiire, 

 xxii, 302, July, 1880.) 



Schuster has given an account of the spectra of lightning observed 

 by him in Colorado during the summer of 1878. He used a direct-vision 

 spectroscope furnished with a slit capable of micrometric movement. 

 A bright line in the focal plane served as a reference mark. The ob- 

 servations were limited to the yellow and the green regions from wave- 

 lengths 5000 to 5800. In making a measurement, the slit was dis- 

 l)laced until the line to be measured was coincident with the reference 

 line. The next morning its position was determined by reference to the 

 solar spectrum. A continuous spectrum was seen many times. Bright 

 nitrogen lines were often seen, those of wavelengths 5002 and 5G81 

 especially. Three bands of wave-lengths, 5502, 5334, 5182, were noted, 

 and a fourth about 5260. Of these, 5182 belongs to nitrogen, and 5592 

 and 5260 are characteristic of the oxygen discharge at the negative 

 electrode. The band 5334 is the most brilliant of the two green bands 

 of the spectrum of oxygen taken at a low temperature. — {Phil. Mag., 

 V, vii, 316, 1879; J. Phi/s., viii, 275, August, 1870.) 



Russell and Lapraik have discovered that many liquids, ordinarily as- 

 sumed to be colorless, give absorption bands when light passes through 

 them on its way to the spectroscope. The phenomenon was first noticed 

 with alcohol; and then it was perceived that water contained in a tube 

 C feet long gave a very distinct absorption band in the orange, corre- 

 sponding very closely with Piazzi Smyth's rain band and with the band 

 seen by Janssen in 330 feet of steam. No variations in this band were 

 observed by varying the source of sujiply, the temperature, or the sub- 

 stances held in solution. Other colorless liquids also gave bands. Am- 

 monia gave four bands; ethylamine also four, but dift'erent in character; 

 hydrogen peroxide, one ; ethyl alcohol, one ; amyl alcohol one; aldehyde 

 and acetic acid, each, one; benzene and toluene, three each; aniline and 

 toluidine, each, three; turpentine, two. These results are regarded as 



