424 



NA TURE 



[March 2, 1905 



being- a tendency for the hydrocarbon and ammonia to be 

 the chief products. 



Glohus for February 23 is a special number containing 

 contributions by friends and admirers of Prof. R. Andree, 

 who reached his seventieth birthday on February 26. 



The third part of the British Journal of Psychology, pub- 

 lished by the Cambridge University Press, has been 

 received. The number contains five papers in addition to 

 a report of the proceedings of the Psychological Society. 

 Mr. Norman Smith discusses Malebranche's theory of the 

 perception of distance and magnitude ; Mr. F. N. Hales 

 considers the materials for the psychogenetic theory of 

 comparison ; Mr. W. G. Smith makes a comparison of 

 some mental and physical tests in their application to 

 epileptic and to normal subjects; Prof. Mary W. Calkins 

 defines the limits of genetic and of comparative psychology, 

 and Mr. C. Spearman makes an analysis of " localisation,'' 

 illustrated by a Brown-S^quard case. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences in March :— 

 March 5. I7h. Sun eclipsed ; invisible at Greenwich. 



7. Ijh. Juno in conjunction with Moon. Tuno 



1° 27' S. 

 9. Jupiter in conjunction with Venus. Venus 5' 30' S. 

 ,, llh. Jupiter in conjunction with Moon. Jupiter 



3° 15' N. 

 12. loh. iim. to iih. 6m. Moon occults 7 Tauri 



(mag. 3-9). 

 17- I2h. 34m. Minimum of Algol (j8 Persei). 



20. 9h. 2m. to 9h. 49m. Moon occults j8 .Vireinis 



(mag. 3-8). 

 ,, 9h. 23m. Minimum of Algol (B Persei). 



21. I2h. Venus at maximum brilliancy. 



24. 7h. Mars in conjunction with Moon. Mars 3° 40' S. 

 ,, Vesta in opposition to Sun. 



Reported Discovery of a Seventh Satellite to Jui-iter 

 —A telegram received from the Kiel Centralstelle announcrs 

 the discovery of a seventh satellite in the Jovian system. 

 The description reads :— 16 magnitude, position on February 

 25 62 degrees, distance 21 minutes, daily motion 60 seconds 

 south-easterly. 



Planetary Tides in the Solar Atmosphere.— In a com- 

 munication published in the Bulletin de la Socim astro- 

 nomtque de France (February, 1905), M. Emile Anceaux 

 discusses the question as to whether the undecennial 

 periodicity of sun-spots may not result from the fluctuations 

 of tides set up in the solar atmosphere by the concerted 

 action of Jupiter, the earth, Venus, and Mercury. He 

 classifies the tides as binary, ternary, and quaternary, 

 according to the number of planets acting in their produc- 

 tion by being in, or near, opposition or conjunction. The 

 ternary tide due to the combined action of Jupiter, Venus, 

 and the earth is supposed to be the most important factor 

 in regulating the appearance of spots, and a curve showing 

 the fluctuations in the strength of this tide, as calculated 

 from the knowledge of the planetary positions, agrees 

 fairly well with the sun-spot curve for the years' iSgi to 

 igo.s. 



Finally, the author arrives at a number of conclusions of 

 which the more important are :— (a) That sun-spots are 

 the indirect consequences of such tides ; (b) that the com- 

 bined action of the three planets especially mentioned 

 •governs the fluctuations of the spot period ; (c) that tnis 

 ternary tide obeys an eleven-year period ; (d) that the 

 i-ariation of the sun-spot period is due to the eccentricities 

 of the planets, chiefly Jupiter. 



The Bruce Photographic Telescope.— The Bruce photo- 

 graphic telescope, with which a number of beautiful photo- 

 graphs of nebulae. Milky Way regions, &c., have already 

 ' en obtained at the Yerkes Observatory, is described in 

 NO. 1844, VOL. 71] 



detail in an illustrated article by Prof. Barnard published 

 in No. I., vol. xxi., of the Astrophysical Journal. 



The telescope was erected, at the cost of .Miss Catharine 

 Bruce, at Yerkes in April, 1904, but has now been dis- 

 mounted and shipped to Mount Wilson, Pasadena, where 

 it is to be used for photographing those regions of the 

 Milky Way not attainable at the former observatory. 



It consists of a 5-inch guiding telescope firmly bolted to 

 two other tubes, which carry photographic doublets of 

 lo-inches and 6j-inches aperture respectively. The focal 

 length of the lo-inch is only 50 inches, and the polar 

 axis of the instrument has been formed by bending the 

 upper part of the iron pier to the required inclination so 

 that the camera may make a complete revolution about the 

 axis without having to be " reversed." For use in different 

 latitudes an iron wedge-shaped section may be introduced 

 between the upper and lower parts of the pier in order 

 to produce the required change of inclination, whilst a 

 special arrangement, whereby the clock motion may be re- 

 versed in two minutes, has been introduced into the 

 driving gear so that the same mounting may be used in 

 the southern hemisphere. 



The lo-inch doublet, by Brashear, gives excellent defini- 

 tion over a field 7° wide, and the scale is such that 

 I inch=i°.i4, or i'' = o.88 inch. The ratio aperture/foca! 

 length = 1/5.03 is that which Prof. Barnard believes to 

 be the best for the purpose for which this instrument was 

 designed. The 6j-inch \'oigtlander doublet has a focal 

 length of 31 inches, and is used in conjunction with the 

 lo-inch for the purpose of verification. Specimen photo- 

 graphs accompany the description, and these testify 

 eloquently to the satisfactory performance of each of the 

 doublets. 



Physical Conditions of the Planets. — In a communica- 

 tion to No. 3992 of the .Astronomische Nachrichten Prof. 

 T. J. J. See deals exhaustively with the methods that he has 

 employed and the results he has obtained in a research on 

 the internal densities, pressures and moments of inertia of 

 the principal bodies in the planetary system. Some of the 

 results obtained in the preliminary discussion of the avail- 

 able fundamental data are of great interest. For example, 

 he arrives at the conclusion that the most probable values 

 for the rotation period and for the oblateness of Uranus 

 are loh. 6m. 40.32s. and 1 : 2$ respectively, whilst for Nep- 

 tune the similar values are probably I2h. 50m. 53s. and 

 I : 4.V 



In the case of the earth, Laplace's law of densities 

 appears to be a natural law, for the value obtained for the 

 oblateness of the outer stratum, or surface, of the globe 

 agrees very well with that obtained as a mean of the most 

 trustworthy of the determinations by more direct methods. 

 The probable value obtained for the pressure acting at the 

 earth's centre is 2383. 152km. of mercury, a quantity so 

 enormous that Prof. See attempts to render it more com- 

 prehensible by suggesting that it is 7S38 times as great 

 as a column of mercury equal in height to the Eiffel Tower. 



The probable pressure at the sun's centre is nearly 212 

 billion atmospheres. A column of mercury acting solely 

 under terrestrial gravitational acceleration would have to 

 be high enough to extend beyond the sun in order that it 

 might exert such a pressure. 



Similar results for the density and pressure at different 

 levels in the planets and satellites are given in two of 

 the tables accompanying Prof. See's paper, and are also 

 shown diagrammatically, whilst a third table shows the 

 ratios of the actual moments of inertia to those of corre- 

 sponding homogeneous spheres. 



Discussion of Central European LoNOiTuoES.^In a 



series of tables published in Nos. 3993-4 of the Astronomischc 

 S'achrichten, Prof. Th. .\lbrei'ht brings together, weighs 

 and tabulates all the longitude results, affecting central 

 European observatories, hitherto obtained. In the first 

 table the longitude differences between 176 pairs of observ- 

 ing stations, as determined since 1863, are thus dealt with, 

 whilst in the second the longitude differences between 

 Greenwich transit circle and numerous other important 

 circles or observatories are brought together. In the third 

 table the corrections to be applied to the differences given 

 in table i., as determined from the discussion of the whole 

 set, are shown. 



