138 



NATURE 



[October i6, 1919 



OUR ASTRONOMICAL COLUMN. 



Ephemeris of Comet 19 196. — Messrs. Braae ana 

 Fischer Petersen give the following continuation of 

 this ephemeris (for Greenwich midnight) in Ast. 

 Nach., 5008 : 



R.A. Decl. Log J- Log ;! 



h. m. s. o - 



II 55 29 « 55N. 9-6856 99440 



Oct. 17 



21 



25 



29 



Nov. 2 



12 3 20 



12 12 36 I 36 N. 97225 00289 



12 22 44 I 43 S. 



12 33 18 4 47 S. 97962 00932 



The comet is in perihelion October 16-9, so it should 

 still be an interesting object, though its distance from 

 the Earth has greatly increased. It is rather incon- 

 veniently placed in the morning sky, but observations 

 of position are much desired. 



The Albedo of Saturn's Rings.— The Astro- 

 physical Journal for July contains a paper on this 

 subject by Mr. L. Bell. It is considered that the 

 very high albedo of the brighter parts of the rings 

 indicates that much of the matter forming them exists 

 in the form of optical dust of dimensions comparable 

 with a wave-length of light. Mr. Bell quotes the 

 familiar fact that many substances appear of a lighter 

 colour when powdered than when in large blocks. He 

 gives 15 km. as the thickness of the main parts of 

 the rings, slightlv greater at the outside of ring B 

 and the inside of ring A. He suggests that there 

 are dust-clouds of exceedingly small density on each 

 side of the ring-plane, to explain the nebulous patches 

 seen when the ring is edgewise. He points out that 

 light-pressure would come into play in the case of 

 this fine dust, and help in its diffusion. It is 

 supposed that there are some larger lumps in the 

 main rings, and by a combination of dynamical and 

 optical arguments fie fixes their diameters as being of 

 the order of 3 metres. Mr. Bell makes use of Prof. 

 Barnard's photographs, and also of those of Prof. 

 Wood in monochromatic light. 



The Selection of Sites for Astronomical 

 Observatories.— The importance of studying atmo- 

 spheric conditions before choosing sites for observa- 

 tories intended for work of a delicate character on 

 the sun or planets is becoming increasingly recog- 

 nised. Prof. VV. H. Pickering gives some interesting 

 details of the station established by the. Harvard 

 Observatory at Mandeville, Jamaica, altitude 2000 ft. 

 {Popular Astronomy, August-September). The air is 

 of such extraordinary clearness that the star 

 yVolantis, magnitude 37, is frequently visible to the 

 naked eye, although its maximum altitude is 1° 40'. 

 A photograph is reproduced, taken with a small 

 stationary camera, which shows a very clear trail of 

 /? Carinas, altitude 2° 40'. 



Prof. Pickering's experience, contrary to the im- 

 pression of many astronomers, is that the seeing is at 

 its best when the air is heavily charged with moisture. 



It will be remembered that much work on Mars 

 has been done at Mandeville in recent years. 



FORTHCOMING BOOKS OF SCIENCE. 

 Agriculture and Horticulture. 



Edward Arnold.— Gardens : Their Form and 

 Design, Viscountess Wolselev, illustrated. Cassell 

 and Co., Ltd.— The Garden M'onth by Month, H. H. 

 Thomas, illustrated ; Garden Handbook for Begin- 

 ners, H. H. Thomas, illustrated. Constable and Co., 

 Ltd.— Forests, Woods, and Trees in Relation to 

 Hygiene, Prof. .\. Henrv, illustrated. — Hodder and 

 Stoughton.— Chemistry and Bacteriology of Agricul- 



NO. 2607, VOL. 104] 



ture, E. J. Ilolmyard, illustrated (The New Teaching 

 Series of Practical Text-books). Hutchinson and Co. 

 — Gardens of Celebrities and Celebrated Gardens, 

 J. Macgregor, illustrated. Macmillan and Co., Ltd. — 

 Science and P'ruit Growing : Being an Account of the 

 Results Obtained at the Woburn Experimental Fruit 

 Farm since its Foundation in 1894, the Duke of Bed- 

 ford and S. Pickering. John Murray. — Conifers and 

 their Characteristics, C. C. Rogers. Oxford Univer- 

 sity Press. — Effects of the Great War upon Agricul- 

 ture in the United States and Great Britain, Prof. 

 B. H. Hibbard ; United States Forest Policy, J. Ise. 



Anthrofology and Arcil?:ology. 



W. E. Harrison (Ipswich). — Pre-Palaeolithic Man, 

 J. Reid Moir. Hutchinson and Co. — The Ruined 

 Cities of Northern Africa, Dr. R. Sturzenbecker, 

 illustrated. Macmillan and Co., Ltd. — An Introduc- 

 tion to Anthropology : A General Survey of the Early 

 History of the Human Race, Rev. E. O. James; The 

 Ila-Speaking Peoples of Northern Rhodesia, Rev. 

 E. VV. Smith and the late Capt. A. M. Dale, 2 vols., 

 illustrated ; Among the Natives of the Loyalty Group, 

 Mrs. E. Hadfield, illustrated. John Murray. — Travels 

 in Egypt and Mesopotamia in Search of Antiquities, 

 1886-1913, Dr. E. A. VVallis Budge, 2 vols., illus- 

 trated. Oxford University Press. — James Tod's 

 -Annals and Antiquities of Rajasthan, edited with an 

 introduction and notes by Dr. W. Crooke, 3 vols., 

 illustrated. 



Biology. 



A. and C. Black, Ltd. — Outlines of the History of 

 Botanv. Prof. R. J. Harvey Gibson. Cassell and 

 Co., Ltd. — Under-water Glimpses of Animal Life, 

 Dr. F. Ward, illustrated. Constable and Co., Ltd. — 

 The Sea Fisheries, Dr. J. T. Jenkins, illustrated. 

 Hodder and Stoughton. — Applied Botany, G. S. M. 

 Ellis, illustrated (The New Teaching Series of Prac- 

 tical Text-books); The Book of a Naturalist, W. H. 

 Hudson ; The Mason Wasps ; The Sacred Beetle ; The 

 Story Book of Birds and Beasts ; and The Story Book 

 of Science, each by J. Henri Fabre, translated n- 

 A. Teixeira de Mattos. Henry Holt and Co. {N(w 

 yorfe).— The Development of the Chick, Prof. F. R. 

 Lillie, new edition. J. B. Lippincott Co. — In Mono- 

 graphs on Experimental Biology and General Physio- 

 logy : The Nature of Animal Light, Prof. E. Newton 

 Harvey ; The Chromosome Theory of Heredity, Prof. 

 T. H. Morgan; Inbreeding and Outbreeding: Their 

 Genetic and Sociological Significance, E. M. East and 

 D. F. Jones; Pure Line Inheritance, Prof. H. S. 

 Jennings ; The Experimental Modification of the 

 Process of Inheritance, Prof. R. Pearl ; Localisation 

 of Morphogenetic Substances in the Egg, Prof. E. G. 

 Conkliii; Tissue Culture. Prof. R. G. Harrison; 

 Permeability and Electrical Conductivity of Living 

 Tissue. Prof. W. J. V. Osterhout; The Equilibrium 

 between Acids and Bases in Organism and Environ- 

 ment, Prof. L. J. Henderson ; Chemical Basis of 

 Growth, Prof. T. B. Robertson; and Co-ordination 

 in Locomotion, .\. R. Moore. Longmans and Co. — 

 A Naturalist's Sketch Book, A. Thorburn, illus- 

 trated. Methuen and Co.. Ltd.— Iron Bacteria, 

 D. Ellis, illustrated. Oxford University Press. — 

 Fungal Diseases of the Common Larch, W. E. Hilev, 

 illustrated. Bernard Qnaritch. Ltd.— Essays in Early 

 Ornithology, J. R. McClvmont, illustrated. G. Pout- 

 ledge and 'Sons. Ltd.— the Wonders of Insect Life, 

 J. H. Crabtree, illustrated. S.P.C.K.— Joseph Dalton 

 Hooker, Prof. F. O. Bower (Pioneers of Progress : 

 Men of Science). Witherby and Co. — A Geographical 

 Bibliography of British Ornithology, H. Kirke .Swann, 

 W. H. Mullens, and F. C. R. Jourdain ; .\ Hand- 



