330 



NATURE 



[August 6, 1903 



tree-planting and to preserve the forests. This is followed 

 by an account of present practice and ideals. The work of 

 the departmental committee appointed by the late Mr. 

 Hanbury is dealt with very fully. The second article is on 

 submarine vessels, and is unsigned. It is accompanied by 

 four plates, and gives a full description of the attempts 

 made to perfect this form of boat, and of the best models 

 now in existence. 



In reviewing Prof. G. P. Merrill's " Stones for Building 

 and Decoration," when the book was first published in 

 1891, we cited it as affording an admirable example of the 

 value of exact scientific knowledge when applied to the 

 treatment of economic questions. The fact that since the 

 date mentioned, as Prof. Merrill points out in the preface 

 to the third edition which has now been issued, there has 

 been a very notable increase in the output of building stone 

 from American quarries, serves to emphasise the real con- 

 nection between the scientific treatment of an industry and 

 its success. The present edition differs ftom the previous 

 ones in containing a revised chapter on methods of testing, 

 a new chapter on the use of drift boulders for building 

 purposes, and five maps showing the geographic distribu- 

 tion of the more important building stones. The new 

 edition is published in this country by Messrs. Chapman and 

 Hall, Ltd., and its price is 21s. net. 



The additions to the Zoological Society's Gardens during 

 the past week include a Chimpanzee (Anthropopithecus 

 troglodytes) from West Africa, presented by Mr. H. Free- 

 land ; a Chacma Baboon (Papio cynocephalus) from South 

 Africa, presented by General Sir Henry de Bathe ; a Rhesus 

 Monkey (Macacus rhesus) from India, presented by Mr. H. 

 Baker; a Levaillant's Cynictis {Cynictis penicillata) from 

 South Africa, presented by Mr. C. Marsh; an Egyptian 

 Ichneumon {Herpestes ichneumon) from North Africa, pre- 

 sented by Dixon Bey; a Nagor Antelope (Cervicapra 

 redunca), a Crowned Duiker (Cephalophus coronatus), a 

 Serval (Felis servai), an African Civei Cat ( Viverra civetta) 

 from West Africa, presented by Sii G. E. Denton, 

 K.C.M.G. ; a Cuckoo (Cuculus canorus), British, presented 

 by Mr. J. O. Pickington ; a Back-marked Snake (Coluber 

 scalaris), South European, presented by Mr. W. H. St. 

 Quintin ; a Common Toad (Bufo vulgaris), European, pre- 

 sented by Mr. H. Verrall ; a Common Mynah (Acrido'theres 

 tristis) from India, a Chameleon Lizard {Chamaeleolis 

 chamaeleontides), two Large Cuban Anolis (Anolis equestris) 

 from Cuba, deposited; three Peacock Pheasants {Polypiec- 

 tron chinquis) from British Burmah, purchased. 



OUR ASTRONOMICAL COLUMN. 



The Spectrum of o Ceti.— No. 41 of the Lick Observ- 

 atory Bulletin is devoted to a discussion of the spectrum of 



Ceti by Mr. Joel Stebbins. 



Using the Mills spectrograph modified to a one-prism 

 instrument, he obtained a series of twenty-five good spectra 

 during the period June, 1902, to January, 1903, in which 

 period the star decreased in magnitude from 38 to 9 o. 

 The spectrograms were obtained on Cramer's " Crown " 

 or " Isochromatic " plates, are 28mm. in length, and extend 

 from A. 3700 to \ 5600. 



Mr. Stebbins finds that the absorption spectrum of Mira 

 is very different from that of the sun ; the calcium lines g, H 

 and K are all present, but g is much stronger than in the 

 solar spectrum. From measurements of six suitable lines 

 he found that the velocity in the line of sight is constant, 

 with a value of -|-66km. A summary of the dark lines 

 discovered indicates the undoubted presence of Fe, Va, Cr 



NO. 1762. VOL. 68] 



and Ca, and the Al and Sr lines are prominent, whilst the 

 presence of Mn and Ti is as yet considered doubtful. 



The general conclusion arrived at is that many of the lines 

 become broader as the star's magnitude declines, and this 

 is undoubtedly true of the g calcium line at A. 422784. In 

 the later photographs some new lines, not definitely co- 

 incident with solar lines, were observed, the chief of these 

 being \ 3990-64, A 4045-16, X 4093-55, and \ 4f)97-o8. 



As regards the continuous spectrum, the photographs 

 show that as the star declines in magnitude the continuous 

 spectrum between \ 4300 and \ 5000 decreases in intensity 

 as compared with that between A. 4000 and A 4300. 



Amongst the bright lines the hydrogen series is un- 

 doubtedly present, although previous observers have doubted 

 the presence of Ha, H/3 and He ; the two latter seem to 

 have become stronger, compared with the other hydrogen 

 lines and the continuous spectrum, as the star became 

 fainter. The presence of bright metallic lines is as yet 

 open to question. In 1898 Campbell observed H7 as a 

 triple line, and it was intended in this research to make 

 polariscopic tests for the Zeeman effect, but, as the line 

 was found to be single on the first spectrograms obtained, 

 no such tests were made. 



Mr. Stebbins discusses the principal theories concerning 

 the remarkable variation in the magnitude of Mira, and is 

 led to the conclusion that it is due to internal forces. 

 Numerous tables and diagrams, and several reproductions 

 of the spectrograms of Mira, accompany the dissertation. 



Photographic Efficiency of a Short Focus Reflector. 

 —In an abstract from No. 539 of the Astronomical Journal 

 Prof. Schaeberle discusses the photographic efficiency of 

 short focus reflectors, and describes some remarkable photo- 

 gr'aphs obtained by himself with a 13-inch parabolic re- 

 flector of 20 inches focus. This reflector is mounted along- 

 side a similar one, which is used as a finder and has an 

 aperture of 12 inches, a focal length of 46 inches, and an 

 eye-piece magnifying 360 diameters, on an ordinary 

 English equatorial mounting, the photographic plate 

 (iV'xS") being placed at the focus of the mirror. 



The resuUs obtained showed that with less than five 

 minutes' exposure the 13-inch revealed stars which are 

 apparently bevond the reach of the 36-inch Lick telescope, 

 and also revealed all the stars obtained by the 3-feet Crossley 

 reflector with two hours' exposure. 



The Ring nebula just shows on plates having had four 

 seconds' exposure, and the central star and Lassell's No. i 

 star (mag. 13) plainly show on an eight seconds' exposure. 

 These photographs disclosed the true form of the Ring 

 nebula, showing that it is a two-branched spiral which 

 commences at the central star, and in a clockwise direction 

 emerges on opposite sides near the minor axis. A repro- 

 duction of a photograph, which has been enlarged 150 times, 

 accompanies the article, and shows the details of the nebula 

 very clearly ; this photograph was obtained on October 30, 

 1902, with an exposure of 128 seconds. 



It has been shown by the photographs obtained that, 

 under favourable conditions and using fast plates (" Seed " 

 Nc. 27), this instrument can photograph stars fainter than 

 the seventeenth visual magnitude in less than five minutes. 



The Godlee Observatory. — In a brochure issued from 

 the printing department of the Manchester Municipal School 

 of Technology, the principal gives a detailed description of 

 the Grubb telescope presented to the observatory connected 

 with the school by Mr. Francis Godlee, of Manchester. 



The mounting is of the twin equatorial type, and carries 

 an 8-inch refractor and a 12-inch Newtonian reflector, besides 

 a 6-inch achromatic doublet intended for astrographic work. 



The refractor is provided with a filar micrometer, a finely 

 divided position circle, and the usual accessories necessary 

 for delicate visual observations. The polar axis is fitted 

 with two R.A. circles, one of which may be set to sidereal 

 time and rotates with the axis, so that the R.A. may be 

 obtained by finding the difference between the readings of 

 the two circles. The driving of the telescopes is performed 

 by the usual clockwork arrangements, and is electrically 

 regulated by a pendulum having a perfectly free movement ; 

 the mounting, is so designed as to permit the instrument to 

 make the whole circumpolar revolution without interruption. 



