800 



SCIENCE. 



[N. S. Vol. IV. No. 100. 



foundation of Bell's work. Unhappily, the 

 hoped-for illumination was not eminently satis- 

 factory. In general, the results of the previous 

 work were found to be capable of extrapolation 

 to low pressures. With some exceptions, the 

 shift of a line for any given element was ap- 

 proximately proportional to the product of the 

 atmospheric pressure to which the arc was sub- 

 jected into the wave-length of the line in ques- 

 tion. The law that the shift is also proportional 

 to the absolute temperature of the melting 

 point of the element was not verified. 



Solar Observations Made at the Boyal Observa- 

 tory of the Roman College During the First Half 

 of 1896 : By P. Tacchini. A tabulation of re- 

 sults showing the distribution of spots, faculae, 

 and prominences upon the sun's surface through- 

 out the half-year. 



Resume of Solar Observations Made at the As- 

 trophysical Observatory at Catalona in 1895 : By 

 A. Mascari. a tabulation similar in form to 

 the preceding, but with more extended discus- 

 sion. 



Certain Considerations Concerning the Accuracy 

 of Eye-Estimates of Magnitudes by the Method of 

 Sequences : By Alex. W. Roberts. Prof 

 Pickering having spoken deprecatingly of the 

 estimation of stellar magnitudes by the un- 

 aided eye, the article appears as a defense of 

 such determinations. In the method pursued 

 by the author stars of the magnitudes 6.8 and 

 9.3 were determined, being respectively on the 

 limit of visibility of the naked eye and a one- 

 inch telescope. The magnitudes of certain com- 

 parison stars were determined by interpolation 

 between these values, and with these the star 

 suspected of variability was compared. Meas- 

 surements of the variable L 5861 show the 

 mean discrepancies of a single observation to 

 be less than 0.04 mag. The relative position of 

 two stars in the field of view is shown to have 

 an important effect upon the estimation of their 

 relative brightness. This personal error is 

 eliminated by using successively direct vision 

 and reversing eye-pieces. The final conclusion 

 is that eye-estimates are as trustworthy as any 

 that are being made photometrically. 



On the Level of Sun-spots: By Edwin B. 

 Frost. A review of the various sun-spot theo- 

 ries in the light of recent investigations. After 



a respectful consideration of the hypothesis of 

 Wilson, that sun-spots are depressions in the 

 photosphere. Prof, Frost points out that there 

 is very little to substantiate it. The existence 

 of the apparent effects of perspective on the so- 

 called penumbra, upon which the theory mainly 

 rests, is doubted by many of the most careful 

 observers. Measurements of the relative ther- 

 mal radiation of spots and contiguous portions 

 of the photosphere show an increase in favor of 

 the spots as they approach the limb of the sun. 

 But the radiation of the spot compared with 

 that from the center of the disc decreases as the 

 spot approaches the limb. This would appar- 

 ently be the case if the spot were composed of 

 radiating matter at a height above the photo- 

 sphere, since in that case its heat would not be 

 so subject to the absorption of the atmosphere 

 on the sun's limb. Again, the velocities of ro- 

 tation upon the sun's surface are in the follow- 

 ing ascending order : velocity of iron vapor, of 

 spots, of faculse. It would appear from this 

 that the elevation of the spots might reasonably 

 be supposed to be intermediate between that of 

 the absorbing iron vapor and faculse, and there- 

 fore above the photosphere. This opinion is sup- 

 ported by the investigations of Wilczynski. 



Researches upon the Arc-spectra of the Metals. 

 11. The Spectrum of Titanium,. II. (Contin- 

 ued from Aug. Ap. J.); By B. Hasselberg. A 

 tabulation of the Titanium lines from 1 3477 to 

 "k 5900. The presence of titanium in the sun 

 is proven, and the lines compared with other 

 determinations. A chart of the spectrum ac- 

 companies the article. 



Minor Contributions and Notes, Harvard col- 

 lege circulai's 10 and 11; notices. 



Review of The Equipment of the Astrophysical 

 Observatory of the Future. G. Johnstone Stoney, 

 A. M., etc.: By F. L. O. Wadsworth. Bibliog- 

 raphy of recent astrophysical literature. 



the AMERICAN GEOLOGIST, NOVEMBER. 



An iron meteorite weighing 19f pounds, 

 found near Arlington, Minn., is described by 

 N. H. Winchell. 



H. W. Fairbanks discusses the age of the 

 California Coast Ranges. Considerable an- 

 tiquity for these mountains is claimed, and a 

 number of profound oscillations are noted, be- 



