Nov. II, 1886] 



NATURE 



2,7 



The additions to the Zoological Society's Gardens during the 

 past week include two Rhesus Monkeys (Macacits rhesus 5 5 ) 

 from India, presented respectively by Col. J. M. McNeile and 

 Mrs. E. White ; a Rose-crested Cockatoo [Cacatita vtolucccnsis) 

 from Moluccas, presented by Miss Townshend Wilson ; twelve 

 Barbary Turtle Doves (Tiirtttr risorius) from Africa, presented 

 by Mr. E. L. Armbrecht, F.Z.S. ; four Copper-head Snakes 

 (Ce>i(hris coti/orli-ix), two Rattlesnakes (Crotalus diirissus), a 

 Ilog-nosed Snake (Hetcrodon platyrhinos) from North America, 

 presented by Mr. W. A.Conklin, C.M.Z. S. ; a Long-nosed Snake 

 {Hetcrodon nasicus] from Indiana, U.S.A., presented by Miss 

 Catherine Hopley ; a Fire-bellied Toad {Bombinator igneiis) 

 from Germany, presented by Mr. G. A. Boulenger, F. Z. .S. ; a 

 liactrian Camel {Camelus bactrinus i),hreA in England, two 

 Eleonora Falcons (Falco eleonom) from North Africa, a Macaque 

 Monkey (.\fiJi-aeiis cynomolgus <J ) from India, deposited; two 

 Mantcharian Crossoptilons {Crossoptilon rnantchiiricitin cj 9 ), 

 two Bar-tailed Pheasants Phasianus reenesi i 9 ) from Northern 

 China, purchased ; ten Barbary Turtle Doves ( Turtur risorius), 

 four Ring Doves ( Turlur communis), bred in the Gardens. 



OUR ASTRONOMICAL COLUMN 

 Stellar Photography at Harvard College. — Prof 

 Pickering has recently presented to the American Academy of 

 Arts and Sciences an important memoir on the work in stellar 

 photography which has been carried on at Harvard College, 

 mainly by aid of an appropriation from the Bache Fund. The 

 memoir commences with a brief sketch of the history of stellar 

 photography, from its origination in 1850, when Mr. J. A. 

 Whipple succeeded in obtaining a satisfactory daguerreotype of 

 Vega with the Harvard 15-inch equatorial, the first stellar 

 photograph ever secured. In 1857, the collodion process having 

 then been introduced, Prof. G. P. Bond resumed the investiga- 

 tion, and showed that photography was capable of doing real 

 work in the observation of double stars. In 18S2 some preli- 

 minary experiments with a lens of 2^ inches aperture were made, 

 and with such satisfactory results that in 1885 the work was 

 resumed with a Voigtiander lens of 8 inches aperture, and about 

 45 inches focal length, that focal length having been selected 

 that the photographs might correspond in scale to the maps of 

 the " Durchmusterung." Of the three departments into which 

 stellar photography may be divided, viz. star-charting, photo- 

 graphing star-trails, and spectrum photography. Prof Pickering 

 has chietly interested himself in the two latter. Star-trails — the 

 images, that is, produced on a plate when the telescope is 

 stationary, or is not following the star with precision — are made 

 exceedingly useful. It furnishes the best method of determining 

 the magnitudes of stars photographically, and the average devia- 

 tion of the measures of the brightness of circumpolar stars on 

 different plates proved to be less than a tenth of a magnitude, a 

 greater accordance than is given by any photometric method. 

 It is Prof. Pickering's intention to obtain determinations of the 

 brightness of all stars north of 30" S. decl. by this method, and 

 the work is now nearly completed. One of the plates taken on No- 

 vember 9, 1885, incidentally affords conclusive evidence that Mr. 

 Gore's Nova Orionis was then much less bright than it was on the 

 night of its discovery, some five weeks later. By photographing 

 on the same plate circumpolar stars near their upper and lower 

 culminations, the means for determining the atmospheric ab- 

 sorption on the nights of observation have been secured. Prof. 

 Pickering has also made some experiments on the applicability of 

 photography to the transit instrument, and concludes that the 

 position of a star may be determined from its trail with 

 an average deviation of only 0-035. Prof. Pickering also shows 

 how star-trails may be made useful in determining the errors of 

 mounting of the photographic instrument. Photographs of 

 stellar spectra have been obtained by simply placing a large 

 prism in front of the object-glass. The spectra of all the stars 

 over an extended area are thus obtained at a single exposure ; 

 an exposure of five minutes giving the spectra of all stars down 

 to the sixth magnitude in a region 10° square. The entire sky 

 north of 23° S. decl. is to be examined in this way, and the 

 work is now far on the way to completion. An exposure of an 

 hour shows the spectra of stars down to the ninth magnitude. 

 A photograph of the Pleiades in this manner brings out the in- 



teresting fact that, with very few exceptions, all have spectra of 

 the same class— a circumstance which seems strongly to confirm 

 the idea of a community of origin. The exceptions may not 

 improbably lie at a considerable distance on this side or the 

 other of the group, and should, as Prof Pickering suggests, 

 receive attention in any study of the parallax of the Pleiades. 

 Prof. Pickering also here discusses several theoretical points of 

 interest, one being the relation between the dimensions of the 

 lens employed and the light of the faintest star that can be 

 photographed with it. He concludes, on the whole, that, where 

 the telescope follows the star with exactness, the limiting amount 

 of light may be assumed as proportional to the aperture divided 

 by the square root of the focal length. Three photographic 

 plates accompany the memoir : the first showing the photo- 

 graphic instrument, the second the trails of a number of close 

 circumpolar stars, and the third several specimens of photo- 

 graphs of stellar spectra, those of Vega, Altair, and of the 

 Pleiades being amongst the number. 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 1 886 NOVEMBER 14-20 



/T7OR the reckoning of time the civil day, commencing at 



^ Greenwich mean midnight, counting the hours on to 24, 



is here employed.) 



At Greenwich on November 14 

 Sun rises, yh. 18m. ; souths, iih. 44m. 3S'5s. ; sets, l6h. iim. ; 

 decl. on meridian, 18° 18' S. : Sidereal Time at Sunset, 

 igh. 46m. 

 Moon (at Last Quarter November 18) rises, I7h. 34m.* ; souths, 

 ih. 43m. ; sets, gh. 37m. ; decl. on meridian, 18° 13' N. 

 Planet Rises Souths Sets Decl. on meridian 



Mercury ... 9 37 



Venus 6 49 



Mars lo 39 



Jupiter 4 35 



Saturn 20 2* 



* Indi( 



•3 17 



II 27 



14 23 



9 57 



4 4 



16 57 ... 25 II S. 



16 5 ... i5 16 S. 



18 7 ... 24 36 S. 



15 19 - 8 15 S. 



12 6 ... 21 19 N. 



5 tliat the rising is that of the preceding evening. 



Occultation of Star by the Moon (visible at Greenwich) 



Corresponding 



Star Mag. Dlsap. Reap. -/.'t^'^-J.^- 



Inverted image 



14 ... 115 Tauri... 

 Nov. h. 



16 ... 13 ... 



■• 4 



5 II 



•39 295 



Saturn in conjunction with and 3° 3' north 

 of the Moon. 



J'ariable Stars 

 Star R.A. DecL 



h. m. „ , h. m. 



U Cephei o 52-2 ... 81 16 N. ... Nov. 18, 3 8 m 



R Arietis 2 9'6 ... 24 31 N. ... ,, 18, »i 



Algol 3 0-8 ... 40 31 N , 14, o 45 m 



„ 16, 21 34 lit 



^Geminorum ... 6 57-4 ... 20 44 N. ... ,, 18, 21 30 m 



U Canis Minoris... 7 35'2 ... 8 39 N. ... ,, 18, M 



R Virginis 12 327... 7 37 N. ... ,, 18, in 



S Ursa: Majoris ... 12 39 'o ... 61 43 N. ... ,, 14, ;// 



U Virginis 12 45-3 ... 6 10 N. ... ,, 18, M 



R Scuti 1841-4... 5 50 N. ... ,, 17, III 



/3 Lyrje iS 45-9 ... 33 14 N. ... ,, 16, o oM 



7) AquilfE 19 46-7 ... o 43 N. ... ,, 16, 19 oM 



5 Cephei 22 24-9 ... 57 50 N 14, o o m 



M signifies maximum ; m minimum. 

 Meteor Showers 

 November 14 is the date of the Leonid shower, R.A. 149°, 

 Decl. 22° N. 



THE EROSION OF THE ENGLISH COASTS 



THE opening meeting of the present session of the Geologists' 

 Association took place last Friday evening at University 

 College, when an address was delivered by Mr. W. Topley, 

 President of the Association and Secretary of the British Asso- 

 ciation Committee on Coast Erosion. The subject of the 

 address was " The Erosion of the Coasts of England and 

 Wales. " 



Mr. Topley, in his address, referred to the great service 



