January 31, 19 18] 



NATURE 



433 



Industrial Colloidal Chemistry, by Prof. E. B. Spear, 

 ;ind a chapter on Colloidal Chemistry and Sanitation 

 l)\ Prof. J. F. Norton; "An Introduction to Theoretical 

 and Applied Colloid Chemistry," by Dr. W. Ostwald, 

 translated by Prof. M. H. Fischer; "Biochemical 

 ('atalvsts in Life and Industry : Proteolytic Enzymes," 

 by Prof. J. Effront, translated by Prof.'S. C. Prescott 

 and C. S. Venable ; "Practical Pvrometrv," by E. S. 

 I'Crry, G. A. Shook, and J. R. Collins; "Hand 

 (irenades," by Major G. M. Ainslie; "Ordnance and 

 (iunnery," by Lt.-Col. W. H. Tschappat ; " Hydro- 

 I'.lectric Power-Stations," by E. A. Lof and D. B. 

 Rushmore; "A Practice Book in Elementary Metal- 

 lurgy," by Prof. E. E. Thum ; "Testing for the Flotation 

 Process," by A. W. Fahrenwald; an enlarged edition 

 of "Practical Instructions in the Search for, and the 

 Determination of, the Useful Minerals, including the 

 Rare Ores," by A. McLeod; "The Development of 

 Forest Law in America," by J. P. Kinney; and re- 

 prints of " Scientific and .Applied Pharmacognosy," by 

 Prof. H. Kraemer, and "Applied and Economic 

 [>otany," by Prof. H. Kraemer. 



OUR ASTRONOMICAL COLUMN. 



The Planet Saturn. — This beautiful telescopic ob- 



■■ ct will be in opposition to the sun on January 31, 



nd will be very favourably placed for telescopic 



scrutiny during the ensuing few months. There is 



evidence to show that much the same phenomena occur 



on Saturn as on Jupiter, and that occasionally dis- 



I turbances on a considerable scale occur in the atmo- 



[ sphere of the former object. Yet it has not been ver>" 



■ successfully observed when we compare the results 



with those obtained with regard to Mars and Jupiter. 



The far greater distance of Saturn and the less con- 



■ spicuous character of the markings are no doubt in 



part responsible for this, but sometimes, as in 1903, 



the spots and irregularities in the belts are very plain 



nd numerous. 



The rotation period of Saturn requires redetermina- 

 tion, for the markings in different latitudes exhibit 

 proper motions. Prof. Hall's white equatorial spot of 

 1876-77 gave a period of loh. 14m., whereas the dark 

 ' and light markings which were visible in the north 

 ( temperate region in 1903 indicated a period of about 

 inh. 38m., or twenty-four minutes longer. 



Unit of Stellar Distance. — As a step towards the 

 \ tension of the decimal system to celestial measure- 

 ,<'nts, and the unification of units in the statement 

 1 stellar distances, it is suggested by M. de Rey Pail- 

 1, de that a convenient unit would be 10'" kilometres 

 1/ Astronomic, December, 1917). A light-year is 

 quivalent to 946 of such units, or approximately 1000, 

 which is a number easily remembered. The parsec, 

 which corresponds to 325 light-years, is ver>- closely 

 3000 units, and the distance of 61 Cygni would be 

 expressed by 5865. On the same system, the mean 

 distance of the earth from the sun is 0015, and that of 

 Neptune 0450. The symbol suggested for the new 

 unit is Us (unitd stellaire), but this does not seem to 

 be well adapted for countries other than France. 



Relativity ANt> Shifts of Fraunhofer Lines.— 

 According to Einstein's theory of relativity, the lines in 

 solar and stellar spectra should Ix^ displaced towards 

 the red bv an amount depending upon the difference in 

 gravitational potential between the gravitational field in 

 which the lines originate and the terrestrial field where 

 the radiation is received. In the case of the sun the 

 theoretical displacement is equivalent to the Doppler 

 displacement due to a radial velocity of 0634 km. per 

 sec, and at A 5000 amounts to o-oio A. With- the 

 powerful instruments now in use in solar observations 



NO. 2518, VOL. 100] 



such a shift of the lines should be easily measurable. 

 The question has been taken up at Mt. VVilson by Dr. 

 St. John, who has selected some of the band lines of 

 cyanogen as the most suitable for the purpose, in 

 consequence of their freedom from displacements due 

 to pressure (Astrophysiccd Journal, vol. xlvi., p. 249). 

 The mean sun minus arc displacement at tlie centre 

 of the sun for the forty-three band lines measured was 

 zero, while for thirty-five lines at the limb it was only 

 + 00018 A. It cannot be assumed, therefore, that the 

 Einstein effect is annulled at the centre by an out- 

 ward radial motion of the solar vapours, as the effect 

 of such a motion would vanish at the limb and the 

 gravitational effect should appear. The observations 

 accordingly give no evidence of a displacement of the 

 lines of the order of magnitude required by the prin- 

 ciple of relativity. 



The "Anni'aire Astronomique " for 19 18. — The 

 current issue of this useful publication maintains the 

 high standard reached in former years. Besides the 

 usual tables relating to the sun, moon, and planets, 

 it includes a series of charts showing the aspect of the 

 heavens in each month, and interesting notes on a 

 great variety of astronomical subjects. A general re- 

 view of progress in the various departments of astro- 

 nomy and meteorology is a valuable feature. The 

 Annuaire is published at 3 francs by the Librairie 

 Ernest Flammarion, Paris. 



PARIS ACADEMY OF SCIENCES. 

 Prizes Proposed for the Year 19 19. 



A/ai^emafiL-i-.— F"rancoeur prize (1000 francs), for dis- 

 coveries or works useful to the progress of pure or 

 applied mathematics. 



Mechanics. — Montyon prize (700 francs), for the 

 invention or improvement of instruments useful to the 

 progress of agriculture, the mechanical arts, and the 

 practical and speculative sciences ; Poncelet prize (2000 

 francs), for work useful to the progress of mechanics. 



Astronomy. — The Lalande prize (540 francs), for 

 the most interesting observation in, or memoir most 

 useful to the progress of, astronomy ; Benjamin 

 Valz prize (460 francs), for work on astronomy under 

 similar conditions to those of the Lalande prize ; G. de 

 Pont^coulant prize (700 francs), for the encouragement 

 of work in celestial mechanics. 



Geography. — Gay prize (1500 francs). The question 

 proposed for .1919 is the study of the physical geo- 

 graphy of North .Africa, and principally Mauritania ; 

 Tchihatchef foundation (3000 francs), for recompense 

 or assistance to naturalists distinguished in the ex- 

 ploration of the lesser-known parts of Asia, excluding 

 British India, Siberia, Asia Minor, and Syria. 



Navigation. — The prize of 6000 francs, for work in- 

 creasing the efficiency of the French naval forces ; 

 Plumey prize (4000 francs), for improvements in steam 

 engines or any other invention contributing to the pro- 

 gress of steam navigation. 



P/jy^/cs.— Kastner-Boursault prize (2000 francs), for 

 the best work on the various applications of electricity 

 in the arts, industry, and commerce ; Gaston Plante 

 prize (3000 francs), to the author of a discovery, inven- 

 tion, or work important in the field of electricity ; 

 Hubert prize (1000 francs), for the best treatise or most 

 useful discovery for the popularisation and practical 

 use of electricity; Henri de Parville prize (1500 francs), 

 for original work in physics; Hughes prize (2500 

 francs), for an original discovery in the physical 

 sciences, especially electricity and magnetism and their 

 applications ; Pierson-Perriri prize (5000 francs), for a 

 discovery in physics. 



Chemistry. — Montyon prize (unhealthy trades) (one 



