8o 



NA TURE 



[November 19, 1908 



Jor the sine and cosine with the special conditions that 

 sin = and coso=i. Dr. Lunn considers that a more 

 elementary treatment can be obtained by starting from the 

 following postulates, viz. the addition formula for the sines 

 of numbers of the straight-angle set, the continuity of the 

 sine and cosine, the assumptions that cos90° = o singo°=i, 

 cos 180°= I, that cos x is not negative between o and 90°, 

 and that if sin xjx has a limit when x vanishes that limit 

 is unity. The last assumption is required to determine the 

 unit of angular measurement. 



In a paper communicated to the Rivisia marittima for 

 March last, and reprinted by the Ofticina poligrafica 

 italiana of Rome (1908), Dr. Eilippo Eredia discusses the 

 prevailing winds in the Straits of Messina, and gives 

 statistics of the observations made at various semaphore 

 stations along the Italian and Sicilian coasts. 



It was announced in last week's Nature that on 

 November 28 Mr. Thayer would give a demonstration at 

 the Zoological Gardens of the obliteralive effects of the 

 costumes of animals. By an error, which we regret, the 

 date was wrongly printed ; it should have been November 

 iS, and not November 28. 



Messrs. Isextiial asd Co., 85 Mortimer Street, London, 

 W'., have issued a list of precision instruments based on 

 the resonance principle, containing information concerning 

 the frequency and speed meters, as well as other instru- 

 ments, constructed by them. 



We have received from Prof. VV. .A. Hordman, K.R.S., 

 a volume containing copies of four addresses delivered by 

 him, in his capacity of president of the Linnean Society, 

 at the anniversary meetings of the society In May of the 

 years 1905-8. The subjects of the addresses were, in the 

 successive years, Linnaeus and artificial pearl formation, 

 natural pearl formation, some fundamentals of sea-fisheries' 

 research, and plankton studies in the Irish Sea. 



OUR ASTRONOMICAL COLUMN. 



Comet Moremol-se, 1908c. — The remarkable changes 

 which have been shown to have taken place in the e.xtent 

 and form of comet 1908c arc well illustrated by a series 

 of photographs taken by M. QuiSnisset at the Juvisy 

 Observatory, and reproduced in the November number of 

 the Bullftin de la Sociiti astronomiquc dc Prance. 



Two photographs taken on .September 30 with equal 

 exposures showed changes in intensity, but were quite 

 eclipsed by one taken the next night, October i, between 

 loh. 48ni. and I2h. 55m. The' trail of a bright star 

 interferes somewhat with the image of the comet's tail, 

 but, despite this, it is seen that the tail has a large, bright 

 condensation at some distance from the head. Erom the 

 coma of the comet several narrow, straight streamers 

 emerge, and then suddenly expand into a bright, nebulous 

 mass which continues for some distance with a much 

 greater breadth and diffuseness than the preceding part 

 of the tail. It almost appears as though a tremendous 

 activity of the head had emitted all this matter and had 

 then subsided, leaving only the normal emission of material 

 to form the straight, narrow streamers. This apparently 

 fluctuating activity may easily be explained by assuming 

 that, during its journey through space, the comet 

 encounters meteor swarms of various densities. 



These changes m.iy be held to account for M. 

 Bigourdan's widely published statement that, at about the 

 time they were photographed, the comet lost its tail. The 

 visual radiations certainly did decrease in intensity, but 

 the photographic rays were not much fainter ; M. 

 Bigourdan's observations were visual. 



Some of the photographs show a tail 17° long, that is, 

 actually about twenty-seven million miles (43,000,000 km.), 

 whilst the diameter of the nucleus is 10' of arc, or actually 

 about 290,000 miles (460,000 km.). 



Numerous photographs, showing changes similar to 

 NO. 2038, \'OI.. 71)] 



those described above, have also been obtained at the 

 Greenwich and Stonyhurst observatories. 



Particulars of the more recent spectrum of the comet 

 are published by MM. Deslandres and Bernard in No. iS 

 of the CoiHptes rendtis (p. 774, November 2). The spectra 

 were obtained with a specially designed spectrograph of 

 10 cm. aperture and 31 cm. focal length, fitted with an 

 ultra-violet glass objective. A prism of the same glass, 

 having an angle of 22°, was placed in front of the objective, 

 and was, at times, supplemented by another of ordinary 

 flint having an angle of 61°. 



The spectra obtained differ on many jxtints from those 

 obtained earlier by Comte de la Baume Pluvinel and de- 

 scribed in these columns. The present workers find that 

 the ratio of ultra-violet to visual rays is abnormal, and 

 that the continuous spectrum is very persistent both in the 

 images of the head and of the tail. The hydrocarbon 

 bands, usually a prominent feature of cometary spectra, 

 especially in the green region, are apparently absent, 

 whilst of the numerous cyanogen bands reported by de la 

 Baume Pluvinel only the two first heads of the ultra- 

 violet group, at A. 38S, were photographed. The three 

 strongest bands appear at about X 456- ■, ^ 426-7, and 

 k 401-3, and are due to some unknown light-source. Many 

 of the bands are double, and MM. Deslandres and Bernard 

 suggest the possibility of this being due to the Zeeman 

 or the Doppler effect, or, maybe, to some new pheno- 

 menon special to comets. 



A New Si'ECTROsconc Laboratory at Pasadena. — 

 Owing to the difficulty of obtaining large supplies of elec- 

 tricity at the Mount Wilson Observatory, Prof. Hale has 

 recently installed a new spectroscopic laboratory at 

 Pasadena, where the laboratory researches necessary for 

 the elucidation of present-day solar problems may be 

 carried out. An illustrated description of the new labora- 

 tory appears in No. 3, vol. xxviii., of the Aslrnphy.<;icai 

 Journal (p. 244, October). 



The main instrument is a 30-feet spectrograph sunk in 

 a waterproof well, 8 feet in diameter, in the concrete floor 

 of the laboratory. The numerous pieces of apparatus for 

 producing radiations are arranged around the well-head, 

 Ihe light being reflected on to the spectrograph slit by a 

 plane mirror. .Among the apparatus briefly described in 

 the present note there is an electric furnace capable of 

 withstanding pressures up to 200 atmospheres, and of 

 giving temperatures up to 3000° C. ; this is to be employed 

 for studying the spectra of such refractory metals as 

 vanadium and titanium at widely different temperatures. 

 .\ transformer capable of producing voltages from 1000 to 

 64,000 has also been installed, whilst a complete outfit for 

 the study of the Zeeman effect in various spectra is in- 

 tended for the laboratory researches which will naturally 

 follow Prof. Hale's recent and remarkable discoveries in 

 the sun-spot spectrum. 



A Large Group of Sun-spots. — .Another large group of 

 sun-spots, made up of a great number of smaller spots, 

 has recently been seen on the solar disc. This group was 

 first observed, at South Kensington on November 6, and 

 was for several days quite easily visible with the naked 

 eye. Another extensive group was first seen, near the 

 limb, on November 12, and was visible to the naked eye 

 on November 17. 



Biograpiiicat. Memoir of .Asaph Hall. — In .April of 

 this year Mr. G. W. Hill read before Ihe National 

 Academy of .Sciences, Washington, a biographical memoir 

 of the late Prof. Asaph Hall giving an account of his 

 life and work. This memoir now appears in vol. vi. of 

 the Biographical Memoirs of the society (pp. 241-309), and 

 is accompanied by a valuable bibliography of Prof. Hall's 

 writings, published between 1858 and 1006, to the number 

 of four hundred and eightv-si.x. 



A Research on the Movement of Comet Wolf. — The 

 results obtained from the first part of a research into the 

 movement of comet Wolf, undertaken by M. Kamensky, 

 of the Pulkowa Observatory, appear in No. 13 of the 

 Bulletin de I'Academie iinperiale des Sciences de St. 

 Pi'lersbourg (October, p. 1041). The present results consist 

 of tables for the calculation of the eccentric anomaly, and 

 they may be used in calculating the perturbations of Faye's 

 and Tempel's comets also. 



