October 21, 1922] 



NA TURE 



555 



tation must have occurred in the introduction " which 

 was meant as such and nothing more." It certainly 

 does not justify the " correction " of the work of 

 highly experienced local officials with not only the 

 people and the country before them, but also the 

 possession of the official technical works and some 

 of the other general books, on which Mr. Brown relies 

 for his facts. 



In a book entitled " Science and Human Affairs," 

 which Messrs. George Bell and Sons, Ltd., will 

 shortly publish, the author, Dr. W. C. Curtis, will 

 recount how the conveniences of daily life and the 

 safeguards to health have been discovered, and the 

 possible bearing of science on human affairs in the 

 future. 



The following catalogues, which should be useful 

 to readers of Nature, have just reached us : No. 95 

 (of Botanical and Zoological Works) from Messrs. 

 Dulau and Co., Ltd., 34 Margaret Street, W.i ; 

 No. 216 (of Periodicals, Collections, Transactions, 

 and Publications of Learned Societies, etc.) from 

 Messrs. W. Heffer and Sons, Ltd., Cambridge ; and 

 No. 372 (miscellaneous, including Natural and Physical 

 Sciences) from Messrs. Bernard Quaritch, Ltd., 

 n Grafton Street, W.i. 



Messrs. Longmans and Co. have in preparation, 

 in four volumes, " A Natural History of the Ducks," 

 by Dr. J. C. Phillips, of the Museum of Comparative 

 Zoology, Cambridge, Mass., U.S.A., which will aim 

 at giving an exact and detailed description of all 

 known species of ducks, mapping their breeding 

 and migration ranges. It will also contain full life- 

 histories of the European and American species. 

 The work will be illustrated in colour and in black 

 and white by F. W. Benson, A. Brooks, and 

 L. A. Fuertes. Vol. 1 is nearly ready for publica- 

 tion. 



Sir Ronald Ross is bringing out, through Mr. 

 John Murray, a work entitled " The Great Malaria 

 Problem and its Solution : an Autobiographical 

 Account," which will give a complete history of the 

 discovery of the relation between malaria and mos- 

 quitoes, showing how malaria is carried from man 

 to man. Another book in the same publisher's 

 announcement list is " Gardening for the XXth 

 Century," by C. Eley, in which attention is chiefly 

 directed to the more permanent features in gardens. 

 The work will contain a list of selected trees and 

 shrubs, with descriptive and cultural notes, and 

 brief chapters upon botany and nomenclature. 



Our Astronomical Column. 



Mercury Visible as a Morning Star. — Mercury 

 will reach its greatest elongation, 18 38' west, in 

 the early morning of October 31, and will be visible 

 before sunrise during the period from about October 

 22 to November 10. The planet will rise about 

 if- hours before the sun, and should be easily visible 

 about an hour before the times of sunrise. Its 

 position will be near the horizon in E. by S., and it 

 will shine with a rosy, fluctuating light about equal 

 to that of a first magnitude star. 



The planet Saturn will be very near Mercury on 

 about October 23, when the distance separating the 

 two orbs will be a little more than 2°. 



Telescopic observations of Mercury are much 

 required, the exact time of the planet's rotation 

 being doubtful. It is a good plan for those observers 

 who do not possess equatorial telescopes to pick up 

 the planet when it is visible to the naked eye, and 

 to get and retain the disc in the field of view of the 

 instrument until some time after sunrise, when it 

 will have risen sufficiently high above the vapours 

 near the horizon to permit the image to be well 

 defined. Mercury certainly presents dusky markings 

 which are capable of being followed when clear 

 weather allows, and the planet offers a much better 

 prospect for successful scrutiny than Venus. 



Comets. — Perrine's periodic comet, 1896 VII. and 

 1909 III., should now be looked for in the moon's 

 absence. The following ephemerides are on two 

 assumptions of the time of perihelion : 



Search should be made near the line joining the 

 two positions for each date. 



NO. 2764, VOL. I lo] 



Mr. Wood sends the following elliptical orbit of 

 comet i<)2 2 a : 



Epoch 1922, Jan. i.o. 



M 



fi 



loge 

 log a 



32 

 V3" 

 16" 



■ 183 37' 



• 274° 3°' 



32 30' 



9'99537i3 

 2-1874524 



■ ■ i"'857 



Period about 1900 years. 



Mr. Wood is at work on a more exact orbit, using 

 photographic positions that extend to April 25 last. 



The Masses of Visual Binary Stars. — The 

 Astronomical Journal, No. 807, contains measures 

 of the parallaxes of several binary stars made photo- 

 graphically at the Sproul Observatory by Messrs. 

 J. A. Milier and J. H. Pitman. Investigation was 

 made as to how far the irregularity of the combined 

 image and the change in relative positions due to 

 orbital motion between the exposures might introduce 

 error. The probable errors seem to be quite as small 

 as for single stars. The parallaxes deduced by other 

 observers are tabulated as well as their own, and 

 masses are deduced and classified according to 

 spectral type with the following results for average 

 mass: B 14-91; A 3-49; F 3-92; G 1-77; K 1-57; 

 M 0-65. Only two M stars were available. 



In conclusion, the advisability is pointed out of 

 obtaining absolute parallaxes of as many binaries 

 as possible by the relative shift of spectral lines due 

 to different motion of the components in the line of 

 sight. The method has already been applied to 

 Alpha Centauri and to Castor, also to Sirius (bright 

 star only). A list is given of 18 stars to which the 

 method might be applied, with the amount of present 

 and maximum differential motion. It is necessary 

 either that both spectra should be visible or that 

 the relative masses should be known. 



