January 9, 1896] 



NATURE 



229 



iccorder, and several improved forms of electric lamps for 

 l.interns. The catalogue of lantern slides should be seen 

 liy all who use the lantern in science lectures. It includes 

 I'rof. Boys' photographs of "flying bullets," sixty-three 

 slides illustrating volcanic action, from photographs by Prof. 

 Johnston Lavis ; photo-micrographs of rock-sections, and 

 many other subjects. The slides are so numerous, and 

 rover so wide a range, that teachers of any and every branch 

 if science will find some in which they will be specially 

 interested. 



We have on our table a number of new editions of books 

 ilready reviewed in Nature. One of these is the secon^i edition 

 'f the " Lehrbuch der Botanik " (Jena: Gustav Fischer), by Drs. 

 Strasburger, Noll, Schenck, and Schimper. This important 

 work was first published in 1894, and the quick call for a second 

 L-dition shows that botanists have not been long in finding out its 

 admirable qualities. Dr. Oscar Hert wig's classic " Lehrbuch 

 iler Entwicklungsgeschichte " (Gustav Fischer) has now reached 

 its fifth German edition. A number of new figures has been 

 added, and results obtained by embryologists in the two years 

 that have elapsed since the publication of the fourth edition 

 have been incorporated in the text. Another fifth edition 

 recently received is " Dynamo- Electric Machinery" (E. and 

 F. N. Spon), by Prof. S. P. Thompson, F.R.S. The chief 

 changes that have been made relate to alternate-current 

 machinery. These and other additions have been made 

 necessary by the development of electric machinery since 1892, 

 when the fourth edition of Prof. Thompson's elaborate work 

 appeared. A second edition has been published of " Dynamo 

 Attendants and their Dynamos" (^Electricity Office), by Mr. 

 A. H. Gibbings. The book is intended for those practical men 

 who have charge of electric lighting plant without knowing 

 much about electrical principles ; it consists, therefore, mainly 

 of hints and advice as to how to manage dynamos, and what to 

 do under those perplexing circumstances which occur in the best 

 regulated dynamo rooms. After six years, a second edition has 

 been published of " Service Chemistry" (W. B. Whittingham 

 and Co.), by Prof. Vivian B. Lewes. The volume is primarily 

 intended to be an exposition of the applications of chemistry in 

 the naval and military services ; nevertheless, a fair proportion 

 of its space is taken up with descriptions of the general principles 

 upon which all technical chemistry depends. Messrs. W. 

 Collins, Sons, and Co. have issued a new edition of " A Manual 

 of Inorganic Chemistry," by' Prof. T. E. Thorpe, F.R.S. Since 

 this manual was first published, twenty-three years ago, it has 

 been frequently reprinted, but the new edition contains so much 

 new matter, and is so greatly altered, that it is practically a new 

 text-book, which will be found even more serviceable than the 

 original one. The work is published in two volumes, which deal, 

 respectively, with the non-metals and metals ; it has been 

 brought thoroughly up to date, and well' records the present state 

 c»f knowledge of the chemistry of the mineral kingdom. 



The additions to the Zoological Society's Gardens during the 

 I>ast week include two Bonnet Monkeys {Macactis sinicus, 6 <J ) 

 from India, presented by Mr. F. Greswolde Williams ; a 

 Common Marmoset (Hapale jacchtis) from South-east Brazil, 

 presented by Captain Pickthorn ; four Pratincoles {Glareola 

 pratincola), four Marbled Ducks {Anas marinorata), South 

 European, presented by Lord Lilford ; a Snow Bunting 

 {Plectrophanes nivalis), European, presented by Mr. J. E. 

 Ilarting ; two Passerine-Parrakeets (Psittacula passerind) from 

 Brazil, presented by Mrs. Robert McCabe ; a Ring-necked 

 I'arrakeet (Falceornis torqtiata) from India, presented by Mr. 

 E. Parrott; a Leadbeaters Cockatoo {Cacatua leadbeateri) from 



NO. 1367. VOL. 53] 



Australia, presented by Mr. B. T. Frere ; two Leopard 

 Tortoises {Testudo pardalis), two Puff Adders {Vipera 

 arietans), an Infernal Snake {Sepedon hamachates) from South 

 Africa, presented by Mr. J. E. Matcham ; a Manatee {Manatus 

 australis) from Demerara, presented by Captain Edward J. 

 Collings ; a Southern River Hog {Potamocharus africantis) 

 from South Africa, presented by Mr. W. Anthony Morgan ; a 

 Black-handed Spider Monkey {Ateles geoffroyi) from Central 



America, a Terrapin (Hydromediisa tectifera) from Rio de 



la Plata, purchased. 



OUR ASTRONOMICAL COLUMN. 



Celestial Photocraphy by Simple Means. — In the 

 hands of Prof. Barnard, the " magic lantern " lens has developed 

 into an instrument of considerable astronomical importance. 

 The lens actually employed by him is a i^ inch doublet of 4 or 

 5 inches equivalent focus, and the scale of the pictures is 

 roughly 10° to an inch. Six beautiful photographs of various 

 parts of the Milky Way taken with this small optical aid are 

 reproduced in the Astrophysical Journal, vol. ii. No. 5, and 

 they admirably illustrate the value of such an instrument in the 

 delineation of extended nebulosities and in photographing large 

 areas of the sky. They are selected from the more remarkable 

 parts of the Milky Way, but Prof. Barnard has obtained a great 

 number of such photographs, and proposes soon to construct a 

 photographic chart from them. The picture of the new nebulous 

 region in Scorpio shows two very obvious streams or "dark 

 lanes" which are almost void of stars, and various peculiarities 

 are presented by the other photographs. 



In the same journal there is a reproduction and an account of . 

 a very fine photograph of the nebula near | Persei (N.G.C. 

 1499) taken with an exposure of six hours by means of 

 the 6-inch Willard telescope, at the Lick Observatory, on 

 September 21, 1895. The nebula is very irregular with 

 numerous condensations, and is remarkable for a small dark spot, 

 about 6' in diameter, in its northern part ; " doubtless a hole in 

 the nebula," says Prof. Barnard. Attention is drawn to the 

 suggestive fact that this nebula lies on the edge of a region in 

 which there is a comparative absence of small stars, as noticed 

 also in the case of most of the large diffused nebulae lately 

 photographed. 



The Constant ok Nutation. — A new determination of 

 the constant of nutation has been made by Dr. Chandler 

 (Astronomical /ottrnal, "Ho. 361). It is based on a discussion 

 of 20,294 observations of stars with the mural circles 

 of Troughton and Jones at Greenwich during the years 

 1825-1848. In order to eliminate errors due to possible slow 

 changes of the angle between the pole and the zenith, whether 

 strictly or irregularly systematic, it has been considered 

 necessary to employ a large number of stars, distributed as 

 uniformly as possible over the entire sky ; and the Greenwich 

 observations offer this facility, while at the same time possessing 

 the necessary degree of accuracy. The adopted mean value of 

 the latitude of Greenwich is 51° 28' 38"-42, and assuming that 

 this is the same in all years, the nutation is found to be 9'''I97. 

 after eliminating the short-period terms of the latitude variation. 

 This assumption, however, is not justified, as the observations 

 indicate a pronounced deviation, which cannot be explained by 

 anomalies of refraction, but must be due to a change in 

 the plar t of the zenith. Although such a . change may 

 possibly be subjective. Dr. Chandler thinks it much more likely 

 to be due to an actual slow change of the latitude. The 

 observations favour an inequality of the mean latitude with a 

 period of about twelve years, and a range of about a quarter of 

 a second. To whatever cause this change may ultimately be 

 ascribed, it is at least necessary to take account of it in evaluat- 

 ing the constant of nutation ; and when this and all other 

 corrections have been applied, the definitive value of the 

 nutation, from the observations with the Greenwich mural 

 circles, is 9"-i92 + o"-oi2. Combining this result with all 

 previous ones which are entitled to any weight at all, the final 

 value becomes 9" "202. The corresponding reciprocal of the 

 moon's mass, in terms of that of the earth, is 81 "80, if 50" '36 be 

 taken for the luni-solar precession. 



