176 



SCIENCE. 



[N. S. Vol. III. No. 57. 



On the Spectrum of Clh'eite Gas : C. Runge and 



F. Paschen. 



The complete results of the writers' investi- 

 gations are now published for the first time. 

 Tables of wave-lengths and of double lines are 

 given in full. When separated into six series, 

 the lines show a striking regularity. Appar- 

 ently there are two pairs of these series, each 

 pair approaching a limit common to its com- 

 ponents. From this and other reasons it is 

 concluded that the gas consists of two elements, 

 for the lighter of which the name Parhelium 

 has been adopted. The hypothesis of two con- 

 stituents is strengthened by the fact that vacuum 

 tubes can be made which show the helium series 

 much less brightly without a corresponding de- 

 crease of intensity in the parhelium series. 

 Moreover, in the spectrum of the sun's limb the 

 stronger of the helium lines are, according to 

 Young, always seen, those of parhelium only 

 about once in four times. 



■On the Oases obtained from Uraninite : 3. Noeman 



LOCKYEE. 



A paper read before the Royal Society con- 

 taining some notes on the new gases recently 

 obtained. These notes consist largely of com- 

 parisons of the spectra of these gases with those 

 of the Sun and stars. 



Outline of an Electrical Theory of Comets' Tails : 



Reginald A. Fessenden. 



The writer advances the theory that a comet's 

 tail consists of negatively charged carbon parti- 

 cles driven from the nucleus by the action of 

 the ultra-violet light of the Sun, its shape being 

 the resultant of four forces : Gravitation acting 

 towards the Sun, electric repulsion of the nega- 

 tive charge on the Sun, attraction due to the 

 positive charge on the comet's nucleus, electro- 

 static repulsion existing between each nega- 

 tively charged particle. The varied cometary 

 phenomena are then examined in the light of 

 this theory. 



Photographic and Visual Observations of Holmes' 



Comet: E. E. Baknaed. 



This is a resum6 of observations made in 

 1892-93. The frontispiece is an enlargement of 

 a photograph of the comet made soon after its 

 discovery. 



The Modern Spectroscope, XV.: F. L. O. Wads- 



woeth. 



In this number of the series is suggested a 

 form of mounting for the concave grating that 

 will overcome its astigmatism so disadvanta- 

 geous to certain forms of astrophysical work. 

 Minor Contributions and Notes. 

 Recent Researches Bearing on the Determination 



of Wave-lengths in the Infra-red Spectrum: 



James E. Keelee. 

 Harvard College Observatory, Circular No. 3 : 



Edwaed C. Pickering. 



THE physical EEVIEW, VOL. III., NO. 4., JAN- 

 UAEY-FEBEUAEY, 1896. 



On the Photometry of Differently Colored Lights, 

 and the 'Flicker Photometer .' By F. B. Whit- 

 man. Based upon the peculiar effect of a 

 flickering light upon the eye (discovered by Prof. 

 Rood), Prof. Whitman has devised a new form 

 of photometer for comparing the luminosities 

 of colored lights and pigments. The construc- 

 tion of the instrument is briefly as follows: The 

 colored surface to be studied is mounted ob- 

 liquely upon a photometer carriage, and is 

 illuminated from a source of light at one end of 

 the bar. On the same carriage is mounted a 

 white disk receiving light from the other end of 

 the bar, and so arranged that it can be rapidly 

 rotated. This disk is given such a shape that 

 it hides the colored surface during half of each 

 revolution. The eye of the observer thus re- 

 ceives light alternately from the colored sur- 

 face and the rotating disk, and at low speeds 

 there is a disagreeable flickering sensation. At 

 high speeds the flickering is no longer noticed; 

 strangely enough the sensation of color practi- 

 cally disappears at the same time, so that it is 

 sometimes found impossible to tell what color 

 is being experimented with. When the speed 

 is sufficiently great the instrument can thus be 

 used as an ordinary photometer, and makes pos- 

 sible a comparison of luminosities without an- 

 noyance from color differences. 



Prof. Whitman describes a number of ex- 

 periments which were made in order to test 

 the instrument, and finds it much more reliable 

 than the ordinary types of photometers. 



The Chemical Potential of the Metals : By W. 

 D. Banceoft. This paper is devoted especially 



