I20 



NATURE 



[July 28, 1910 



his appointment to tlie chair in these subjects in the Uni- 

 versity of Paris. The list of Prof. Picard's worlis and 

 papers on mathematical subjects occupies a very large part 

 of the memoir, which also contains an appreciation of his 

 work by Prof. Henri Poincar^, delivered in 1888 in pre- 

 senting him with the grand prize of the Paris Academy of 

 .Sciences for Mathematical Science. 



The first issue of a new annual, entitled " The Green 

 Book of London Society," has been received. Its sub- 

 title describes the volume as a directory of the Court, of 

 society, and of the political and official world, including 

 celebrities in art, literature, science, and sport, with many 

 other subjects of current interest. The editors of the com- 

 pilation are Mr. Douglas Sladen, who, it will be remem- 

 bered, compiled "Who's Who," and Mr. W. Wigmore. 

 Under science are given lists of some men of distinguished 

 eminence in the London scientific world, with the researches 

 and discoveries which have made them famous ; the most 

 important scientific and engineering institutions ; and some 

 of the chief scientific periodicals. The book runs to 487 

 pages, and is published by Messrs. J. Whitaker and Sons, 

 Ltd., at 5.?. net. 



The sixth edition, revised, of Dr. Bernard Dyer's small 

 handbook on " Fertilisers and Feeding Stuffs : their. 

 Properties and Uses," has just been published by Messrs. 

 Crosby Lockwood and Son, price one shilling net. Short 

 descriptions have been added of the two new fertilisers — 

 nitrate of lime and calcium cyanamide — in which atmo- 

 spheric nitrogen is fi.xed, but the practical disadvantages of 

 their use are pointed out. Of the former Dr. Dyer 

 remarks : — " It has a serious practical disadvantage in its 

 deliquescent property, which makes it necessary to sow it 

 immediately the air-tight packages in which it is sent out 

 are opened, and it cannot be conveniently sown in moist 

 weather." Calcium cyanamide is also unpleasant to sow. 

 Dr. Dyer's book is a manual from which practical farmers 

 can obtain many useful hints as to profitable procedure in 

 fertilising the soil for different crops and feeding the stock. 

 The text of the Act of 1906, referring to fertilisers and 

 feeding stuffs, is printed in full, together with the regula- 

 tions of the Board of Agriculture and Fisheries for the pro- 

 tection of farmers from the supply of adulterated materials. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences in August: — 

 Aug. 2. Ilh. iSni. Moon in conjunction with Venus. 

 (Venus 4° 8' S.). 



8. 9h. ilm. , Minimum of Algol (/3 Persei). 



9. 6h. 26m. Moon in conjuncdon with Jupiter 



2° 34' S. 

 10. I2h. 46m. Venus and Neptune in conjunction. 



Venus 0° 27' N. 

 II — 13. Maximum of August Perseid display. Radiant 



44° + 57°- 

 14. Venus. Illuminated portion oi disc = o"S89. 

 16. Saturn. Major axis of outer ring = 43 '21". Minor 



axis= 13-51". 

 25. 5h. 46m. Moon in conjunction with Saturn. 



Saturn 1° iS' S. 



27. I4h lim. to I4h. 54m. Moon occulls t Tauri. 



(Mag. 4-3). 



28. loh. 53m. Minimum of Algol (8 Persei). 

 30. lih. Mercury at greatest elongation, E. 27°. 



Subjective Phenomena on Mars. — In No. 4427 of the 

 Astronomische Nachrichten M. Antoniadi returns to the 

 discussion of the objective reality of the dark band seen 

 circling the Martian snowcap. He previously directed 

 attention to the fact that this band was not visible on 

 photographs of the planet, and suggested that its appear- 

 ance during visual observations was simply an effect of 



NO. 2126, VOL. 84] 



contrast. This argument was weakened by the possibilitv 

 of photographic " spreading " in the sensitive film being 

 sufficient to account for the obliteration of the dark band. 

 But M. Antoniadi now points out that on the photographs 

 taken with yellow screens during the last opposition, the 

 caps are no more intense than the " continental " areas, 

 and from this he suggests that " spreading " is negligible. 

 Vet the dark band is not to be found on these photographs, 

 and therefore, if the premises are true, it appears that its 

 visibility in visual observations is only a subjective 

 phenomenon. 



The GENE.SIS of Various Lunar Features. — In the 

 Comptes rendus, No. 2 (July 11), M. Puiseux discusses the 

 probable origins of the circles and of the angular outlines 

 of lunar crevasses shown in the polar regions of the moon 

 on the concluding sheets of the great photographic atlas of 

 the moon published by the Paris Observatory. He points 

 out that many of the circles appear in chains, of two or 

 more, parallel or perpendicular to the meridian. Where 

 two of these circles intersect, the point of junction i« 

 marked by a small crater or a considerable elevation, and 

 M. ^Puiseux believes that this is evidence against Faye's 

 theory that the bourrelets were formed by repeated periodic 

 overflowings which filled in the circle. Such differences 

 of level as are now revealed would be incompatible with 

 this theory. On the same plate (Ixvi.) is seen a number 

 of circles aligned on, or across, a meridian, and joined 

 by a high, narrow ridge, and M. Puiseux considers that 

 these are evidence against the meteoric bombardment 

 theory. 



Near the northern pole the geometrical contours of 

 circles are exceptional, and angular features predominate. 

 The ridges here are found to be in echelon, and M. 

 Puiseux considers that the sharp angles were formed where 

 previous ejecta prevented the eruptions from following the 

 general line of weakness to which, however, the sub- 

 sequent eruptions returned, thus producing the echelon 

 form. 



Halley's Comet. — A preliminary account of the observa- 

 tions made by an expedition which journeyed to the Pic du 

 Midi to observe Halley's comet is given in No. 2 of the 

 Comptes rendus (July 11) by MM. G. Millochau and H. 

 Godard. 



Arrangements were made to photograph, regularly, the 

 comet and its spectrum, but they were sadly interfered 

 with by bad weather. No spectrograms were secured, but 

 several good photographs were taken with a Zeiss " astro- 

 planar " lens having a large field. The photograph secured 

 on May 29 showed a bright condensation, detached from 

 the nucleus, which at 2° from the head became broader, 

 and was prolonged some 8° into the tail. The photograph 

 of May 31 shows a secondary nucleus at a distance of 17" 

 from the primary. 



A long summary of the numerous observations made at 

 different places during the passage of the comet is pub- 

 lished in the July number of the Bulletin de la SociHi 

 astronomique de France, and is illustrated by a number 

 of drawings and photographs. 



The Gnomon in Ancient Astronomy. — .\11 who are 

 interested in the early days of astronomical observation 

 will find an article by M. Jules Sagaret, published in 

 No. 17 of the Revue scientifigue, full of interest. M. 

 Sagaret discusses at length the role played by the gnomon 

 in the observations made by the ancient Chinese, Baby- 

 lonians, Egyptians, &c., for the determination of time and 

 season, especially of the solstices, and shows that in a 

 vertical bamboo rod the Chinese of about the second 

 century B.C. found a, comparatively, very effective astro- 

 nomical instrument. 



The Leeds Astronomical Society. — The Journal and 

 Transactions of the Leeds Astronomical Society for 1909 

 (No. 17) shows that this society is endeavouring to 

 popularise the study of astronomy with its wonted vigour. 

 In addition to numerous interesting papers read by 

 members at the meetings of the society, there are a number 

 of reprints of popular articles contributed to various publi- 

 cations. .Among these are articles on current phenomena 

 contributed bv Messrs. Whitmell, Scrivpn Bolton, and 

 Ellison Hawks, and a series of articles by Mr. Elgie which 

 appeared in T.P.'s Weekly over the pseudonym 

 " F.R.A.S." 



