December 17, 1891] 



NATURE 



59 



The additions to the Zoological Society's Gardeni during the 

 past week include a Sooty Mangabey {Cercocebtts ftiliginosus 9 ) 

 from West Africa, presented by Mr. H. E. Dampier, J. P. ; 

 a Rufous-necked Weaver- Bird {Hyphantornis textor i) from 

 West Africa, presented by Commander W. M. Latham, R.N., 

 F.Z. S. ; a White Stork {Ciconia alba), European, presented by 

 Mr. Walter Chamberlain, F.Z.S. ; eighteen Grenadier Weaver 

 Birds [Euplectes oryx), ten Golden-backed Weaver Birds 

 {Pj/rontelaiia aiirea), nine Black- capped Weaver Birds 

 {Hyphantornis nigriceps), four Red-bellied Waxbills (Estrelda 

 rufiventris), three Triangular-spotted Pigeons {Columba guinea), 

 four Dwarf Chameleons {Chameleon pumilus) from South 

 Africa, presented by Mr. R. W. Murray. 



OUf< ASTRONOMICAL COLUMN. 



Jupiter and his First Satellite. — A series of observa- 

 tions of spots and markings on the planet Jupiter were communi- 

 cated to the Royal Astronomical Society at the November 

 meetintj by Mr. Barnard. A careful study of numerous details 

 observed during a period of twelve years has led to the con- 

 clusion "that the red colour of any of the markings is an 

 indication of their age ; or in other words, when a spot or 

 marking (other than the white spots) first appears it is dark or 

 black, but after some time turns red." Several examples are 

 given of this transition, and the great red spot seems to be no 

 exception to the rule. Measurements of transits of the broken 

 chain of small black spots just north of the north equatorial belt, 

 discovered by Mr. Barnard during the present year, show that 

 the spots have a very large relative motion, for they complete a 

 revolution around Jupiter in about thirty-seven days. The 

 oblong dusky spot discovered near the great red spot last year 

 is diminishing its longitude by about o''54 per day, and so com- 

 pletes a revolution relatively to the latter in about [67 days. 

 This, and other new red markings in the southern hemisphere, 

 seem to have their origin in the region of the jjreat red spot. 

 Their period of rotation is about the same as the round white 

 spots in the same hemisphere, the longitudes of which diminish 

 by about o -6 per day. The observations show that the great 

 red spot is stationary in longitude, and possibly shorter and 

 broader now than in 1880. Further observations of the first 

 satellite have been made in order to throw light upon the 

 apparent duplicity of this body in transit, distinctly seen by Mr. 

 Barnard on September 8, 1890. It is noted : — " The pheno- 

 mena seen on these occasions would rather discourage the idea 

 ©factual duplicity. At these times the satellite has appeared 

 egg-shaped when in relief on the dark belt. ... I am con- 

 fident that this particular phase, and perhaps also that of 

 apparent duplicity, is explained by a bright belt on the satellite 

 or by darkness of the polar regions, which is the same thing." 

 Mr. Stanley Williams has suggested that the phenomenon 

 observed on September 8, 1890, may have been due to the 

 satellite having been seen in transit as a dark spot close to a 

 dark spot on; the surface of Jupiter which transited at the 

 same time. 



Spectra ok the Sun and Metals. — Some extremely 

 fine comparative photographic spark-spectra of the sun and 

 metallic elements were exhibited by Mr. F. McClean at the 

 meeting referred to in the above note. The spectra extend, in 

 six sections, from A 38CX5 to A 5750 — that is, from about L of the 

 solar spectrum to near D. They are divided into two series — 

 one containing spectra of the sun, iron, platinum, iridium, 

 osmium, palladium, rhodium, ruthenium, gold, and silver ; the 

 other containing spectra of the sun, iron, manganese, cobalt, 

 nickel, chromium, aluminium, and copper. The scale of wave- 

 length adopted is that of Angstrom's map. Since the spark was 

 taken in air all the spectra have air-lines running through them. 

 The purest materials obtainable were used as electrodes : 

 nevertheless a large number of lines due to foreign substances 

 appear on the photographs. The commonest impurity is 

 calcium, its lines being present in very nearly all the spectra. 

 No attempt has been made to eliminate the lines having their 

 origin in such impurities ; hence, as Mr. McClean remarks, it is 

 impossible "to obtain any complete results from these two 

 series of photographs alone. Photographs of the spectra of all 

 the common oxidizable metals, and particularly of calcium, 

 barium, magnesium, and titanium are first required." 



Astronomische Nachrichien, No. 3068, contains the following 

 ephemeris for the Comet Tempelg- Swift for I2h. Paris mean 

 time : — 



NO. I 155, VOL. 45] 



Astronomische Nachrichten, No. 3069, contains a paper by 

 Prof. Pickering on the distribution of energy in stellar spectaa. 

 Since stellar magnitudes obtained by various processes, such as 

 photography, eye-observations, i<c., cannot be co upared when 

 the light of stars is of different colours, the method he pro- 

 poses is to adopt a single wave-length in the spectrum to which 

 all intensities should be referred, a curve or series of numbers 

 being necessary to give a measure of the rays of each different 

 wave-length. For rays of different wave-lengths he says : 

 " The intensities may be determined by comparing the densities 

 of different portions of the photographic spectrum." The line 

 fixed upon was that of the hydrogen line G, "as it is near the 

 centre of the photographic spectrum." The photographs he 

 employed were those forming part of the Henry Draper 

 Memorial, all taken under similar conditions, and in each one 

 separately twenty points were taken and compared by com- 

 parison with a standard photographic wedge. Each of the 

 measures thus obtained was converted into logarithmic intervals, 

 and the measure, corresponding with that of the hydrogen 

 line G of wave-length 434, was deducted. By subtracting 

 the values of the logarithm of the energy of the solar light, the 

 remainder showed " the excess or deficit of energy of the star 

 as compared with that of the sun, eliminating the various sources 

 of error enumerated above." In the table below we give the 

 results for three stars as obtained by Prof. Pickering : — 



The values in the second column representing the logarithm 

 of the energy of the solar light, while those in the last one 

 represent the energy of sunlight itself. Thus in the case of 

 a Orionis, the energy for the wave-length 390 is represented 

 by — 0-57, sunlight being 0-55. The absolute energy is found 

 " by adding the tabular number to that given for sunlight in 

 the second column," so that we have - 0-26 - 0-57 = — 0-83, 

 corresponding to a ratio of 0-15. Thus the energy of the light 

 of a Orionis of wave-length 390 is only about one-seventh of 

 that of wave-length 434. 



In this number, al-;o. Mr. Truman Saffard contributes a paper 

 on the observation of North Polar stars in the vertical of Polaris. 

 After mentioning the difficulty of observing polars in the day- 

 time, of connecting other polars with double transits of Polaris, 

 and of the independence that now exists in the various Polar 

 catalogues, he describes a method which tends to eliminate 

 many of these deficiencies. It consists in adjusting a transit so 

 that Polaris will be near its centre wire at eastern elongation, 

 which takes place about igh. 23m. sidereal time, and the two 

 stars Camelopardalis 25 H and Schwerd 1 172 (Carrington 2965), 

 which pass the same vertical within about half an hour of this 

 time, the latter above Pole, earlier than the Pole-star reaches 



