2.S6 



NA TURE 



[July io, 1690 



vulturina), three Mitred Guinea Fowls {Numida mitrata) from 

 East Africa, presented by Mr. George S. Mackenzie ; a Tawny 

 Owl {Syrnium ahtco), British, presented by Mr. G. Gurney ; 

 a Long-eared Owl {Asio otus), British, presented by Miss Muriel 

 Hele ; a Feathery-footed Owl {Athene plumipes), a Black and 

 White Jackdaw {Corvus daiirka) from Newchang, South 

 Mantchuria, presented by M. J. De La Touche ; two Indian 

 White-Eyes {Zosierops palpebrosus) from India, a Yellow-winged 

 Sugar- Bird {Cesreba cyanea $, ) from Brazil, a Dufresne's Waxbill 

 {Estrelda dufresnii) from South Africa, six Vulturine Guinea 

 Fowls {Numida vulturina) from East Africa, deposited ; a 

 Plumbeous Fish-Eagle {Polioa'etus plumheus) from North-west 

 India, two Golden-headed Parrakeets {Cyanorhamphus auriceps) 

 from New Zealand, a Green-winged Dove ( Chalcophaps indica 9 ) 

 from India, purchased ; two Emus {DroincBus novcB-hollandice), 

 received in exchange; a Yzk{Poephagus gruntiiens $ ), aViscacha 

 {Lagostomus trichodactylus), born in the Gardens, 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 

 Sidereal Time at Greenwich at lo p.m. on July lo = 

 I7h. 15m. Ss, 



Remarks. 



(i) Unfortunately this interesting object only attains a low 

 altitude in this country, but it is quite possible that there may 

 be some nights on which spectroscopic observations may be 

 made. It is the object known as the " Trifid Nebula," which 

 is thus described in the General Catalogue :— " A very remark- 

 able object ; very bright ; very large ; trifid ; double-star in- 

 volved." For a further description observers may refer to 

 Herschel's " Outlines." The spectrum was recorded as "con- 

 tinuous " by Captain Herschel in 1868, but in the same year it 

 was observed by Prof. Winlock at Harvard College, and found 

 to contain bright lines. This observer records : " Spectrum of 

 the multiple star continuous, with many bright lines and some 

 bands ; one end of spectrum at A 428o± . . . one bright line 

 seen by C. S. Peirce at A.498o±." I am not aware that any 

 further observations of the spectrum have been made, but these 

 observations should certainly be repeated with as large an aper- 

 ture as possible. There can be little doubt that the line near 

 A. 4980 is really the chief nebula line at A. 500. The appearance 

 of bands is especially interesting, as indicating that only a 

 relatively low temperature can be in question. 



(2) The spectrum of o Herculis is probably well known to 

 everyone who possesses a telescope ?nd spectroscope. It is a 

 very beautiful one of Group II., all the bands being very wide 

 and dark, giving an appearance of alternating bright and dark 

 bands. From the observations of Prof. Lockyer, Mr. Maunder, 

 and myself, there can now be little doubt that we have here to 

 deal with a mixed spectrum of bright carbon flutings and dark 

 metallic ones. One bright band in the green is coincident with 

 the chief carbon band, and has, moreover, the same appearance. 

 The measures of the dark bands in the green and yellow by 

 Vogel and Duner show close coincidences with the flutings of 

 manganese (A 558 and 586) and lead (A 546), and I have con- 

 firmed these by direct comparisons. The principal object in 

 inserting the star in this column is to remind observers that 

 this is a good opportunity for them to demonstrate for them 

 selves that in stars of this type we are dealing with cometary 

 conditions, as indicated by the carbon radiation. 



(3 and 4) These stars have spectra of the solar type and of 

 Group IV. respectively (Gothard). 



(5) Duner describes the spectrum of this star as one of Group 



NO. 1080, VOL. 42] 



VI., in three zones, of which the green is the brightest. He 

 states that the spectrum is rather feebly developed, but it is not 

 clear whether this is due to the faintness of the star, or that the 

 bands are narrow as compared with other stars of the group. If 

 the latter, the star may be one of the long-required connecting 

 links between stars of this group and stars of the solar type. 



(6) The spectrum of this variable does not appear to have 

 been recorded, although its magnitude at maximum is about 5. 

 The minimum is irregular, 6'o-8*5, and the period, according 

 to Schmidt, is about 168 days. There will be a maximum about 

 July 14. A. Fowler. 



Secular Inequalities in the Moon's Motion. — In the 

 Astronomical Journal for June 20, Prof. J. N. Stockwell con- 

 tributes the abstract of a discussion of the problem of the secular 

 variation of the motion of the moon's perigee and node. The value 

 found for the secular variation of the mean longitude of the 

 moon's node does not differ very materially from that found by La- 

 place and subsequent investigators. But it is otherwise with the 

 secular equation of the motion of the moon's perigee ; and if the 

 value Prof. Stockwell has obtained for the secular motion of the 

 moon's perigee is nearly correct, the value found by Laplace and 

 his immediate successors cannot be regarded even as a first 

 approximation to the value of that motion. 



If the mean longitude of the moon's perigee be denoted by w, 

 and the number of centuries from a given epoch by i, the varia- 

 tion Ao) of the mean longitude of the perigee at any number of 

 centuries from the epoch are quoted by Airy as follows : — 



Laplace - 30'55«^ 



Borg and Burckhardt - 29"98j^ 



Damoiseau - 39702^ 



Plana - 40-23j2 



Hansen - ^g-iS?^ 



Hansen - 36-3n'l 



Notwithstanding this agreement of the results of other in- 

 vestigators. Prof Stockwell has found, by direct calculation, 

 that Ato is very nearly expressed by the formula 



Aw = -f i5"-6ii2 ; 

 and since the motion of the perigee is direct, it follows that this 

 motion is accelerated instead of being retarded from age to age, 

 as has been hitherto supposed. The application of the result 

 to the discussion of some ancient eclipses is reserved for a future 

 communication. 



Annular Eclipse of June 17. — The current number of 

 the Comptes rendus contains a letter from M. A. de la Baume 

 Pluvinel to M. Janssen, respecting his observations at Canea 

 Photographs of the annular and partial phases were obtained, 

 and will be of service in determining the diameters of the surt 

 and moon. M. Pluvinel also finds that there is no difference 

 between photographs of the spectrum of the edge of the sun 

 during the annular phase and the ordinary solar spectrum. It 

 is interesting to note that during the eclipse the temperature fell 

 from 33"-4 to 27°-4 C. 



THE ETHNOLOGY OF THE GAMBIA REGION. 



•yHE Governor of the Gambia, in his last Report, devotes a 

 •^ long section to an account of the African tribes connected 

 with that settlement, of which the following is a brief summary : — 

 Mandingoes. — The head -quarters of this extensive and power- 

 ful race lie in the mountainous district near the sources of the 

 Niger and the Gambia, extending as far as Kong. From this 

 region they overran the surrounding country westward to Bam- 

 bouk, and still pushed on, until the banks of the Gambia, as far 

 as the sea, more or less, fell under their sway. At the present 

 moment the principal countries on the north bank of the river 

 are occupied mostly by Mandingoes, and the dominant tribes in 

 Combo, on the south bank, are also of the same race, though the 

 heathen Jolas in the bordering Fogni country are able to hold 

 their own against them. They practically control the trade of 

 the lower river. Three-fourths of the ground-nuts hitherto cul- 

 tivated have been grov/n by them ; the export of bees'-wax seems 

 to be also dependent upon the Mandingoes, who bring it down 

 from the interior of the Jola country. They also bring cattle 

 and hides into the market, and cultivate cotton largely, which 

 their women spin and weave into the country cloths which play 



