April 9, 1897.] 



SCIENCE. 



591 



octopus cast ashore on the Florida coast, some 

 months since, it has been shown that the mass 

 resembles not an octopus, but rather the sub- 

 stance which forms the head of a sperm whale. 

 The nature of the original animal is still in 

 doubt, since no known species could have 

 yielded a mass of this size, entirely free from 

 any bony structure. 



THE ASTROPHYSICAL JOURNAL, FEBEUAEY. 



The Absorptian of Light ccs a Determining Factor 

 in the Selection of the Size of the Objective for the 

 Great Refractor of the Potsdam Observatory : By 

 H. C. VOGEL. The author discusses the effect 

 of absorption upon the ' light-grasping power ' 

 of objectives of various apertures. The first 

 part of the paper deals with the experiments 

 for the determination of the absorption of the 

 various varieties of glass available for large 

 objectives. The second part consists of the 

 application of the constants thus obtained to 

 the detei-mination of dimensions. Assuming 

 the ratio of diameter of lens to thickness to be 

 between six and seven, it is shown that an 

 increase in aperture above 80 cm. gives very 

 little corresponding increase of light. This is 

 due to the additional absorption which is en- 

 tailed by the increased thickness. An increase 

 in diameter from 35 cm. to 80 cm. multiplies 

 the light-gathering power by four, while a further 

 increase to 100 cm. adds another factor of only 

 1.4. In view of the rapid increase in cost of 

 a telescope, corresponding to an increase in 

 size, and the smallness of this last factor, Dr. 

 Vogel considers 80 cm. as about the most eco- 

 nomical diameter. As the telescope is to be 

 used chiefly for astrophysical work, it is to be 

 corrected for photographic rays, and it is the 

 absorption of these which determined the di- 

 mensions. The life partner of the great re- 

 fractor is to be a visually corrected finder of 

 50 cm. aperture. 



The Spectrum of Ptcppis: By E. C. Pickek- 

 ING. As was announced in jff. C. 0. Circular, No. 

 12 (Ap. J., Dec, 1896), the spectrum of 

 Puppis contains two rythmical systems of dark 

 lines, one being the known series due to hydro- 

 gen. It was also announced that the other series 

 is governed by a law somewhat resembling 

 Balmer's law for hydrogen. In the present 



paper the writer points out that by a modifica- 

 tion, Balmer's formula may be made to satisfy 

 both series. The formula as ordinarily written 



to" 

 (for Rowland's scale) is a = 3646.1 —^ — 2 ' where 



TO ^ 3, 4, 5, 6, etc., substituting ^^ n = m we ob- 

 tain A -- 3646.1 ^ ..„ i which gives the hydro- 

 gen lines when n ^ 6, 8, 10, 12, etc., and the 

 lines of the newly discovered series when 

 n, = 5, 7, 9, 11, etc. In the light of this re- 

 markable relation it seems probable that the 

 new series is, in fact, due to hydrogen under 

 some physical condition so far unknown upon 

 our globe. 



On the Spectrum of Puppis : By H. Kayser. 

 In connection with this spectrum Professor 

 Kayser calls attention to the fact that hydrogen 

 is the only element which has, until now, been 

 considered to have only one series of lines. In 

 every other case where series have been found 

 to exist, there are two converging approx- 

 imately to the same limit, each satisfying a 



formula of the type _ ^A — Bm"^ — Cm~^ 



where m = 3, 4, 5, 6, etc. The alkali metals 

 have in addition a third series, brighter than 

 these two. It has been generally supposed here- 

 tofore that the ordinary hydrogen spectrum 

 consisted of this series. Certain considerations 

 however seemed to contradict this. The 

 newly found series in Puppis now fits in very 

 neatly, converging approximately to the same 

 point as does the old one. In the light of these 

 developments more accurate measurements of 

 the positions of the new lines will be of great 

 interest. 



On the Effect of Pressure in the Surrounding 

 Gas on the Temperature of the Crater of an Elec- 

 tric Arc. Correction of Results in Former Paper : 

 By W. E. "Wilson and G. F. Fitzgeeald. 

 "The primary object of this research was to 

 determine, if possible, whether the temperature 

 of the crater in the positive carbon varies when 

 the pressure in the surrounding gas is changed. ' ' 

 The result is interesting as bearing directly 

 upon the mooted question as to whethet the 

 temperature of the crater is that of boiling car- 

 bon. If such were the case we should expect 

 a rise in the temperature of the crater with in - 



