Oct. 17, 1889] 



NATURE 



597 



1600°, the highest temperature attained, the value 4*08 wa« 

 obtained. It therefore appears that for 600° over iooo° a very 

 small amount of dissociation occurs, probably owing to the 

 influence of a small platinum tube in which the chloride was 

 introduced, as a minute quantity of an alloy of aluminium and 

 platinum was afterwards found. Hence the molecules of AICI3 

 must be remarkably stable. The first of the experiments by the 

 method of Dumas was conducted at the temperature of boiling 

 nitrobenzene, 209 "^ ; at this temperature the density was 99. 

 At the temperature of boiling eugenol, 250°, 9*62. At 301°, in 

 vapour of diphenylamine, 9'55. In mercury vapour, at 357°, 

 9*34. In volatilized antimony tri-iodide, at 401°, 9*02 ; while at 

 the temperature of boiling sulphur, the density, according to 

 this method, had diminished to 879. From these results the 

 Swedish experimenters conclude that the vapour-density of 

 aluminium chloride decreases continuously and almost regularly 

 up to 800", when it becomes practically constant for four or five 

 hundred degrees of temperature, and that although the value 

 9*2 is found somewhere between 2CO° and 400°, yet this value 

 does not remain constant for a sufficient interval of tempera- 

 ture to enable us to assert the existence of molecules of the 

 composition AlXlg. 



The additions to the Zoological Society's Gardens during the 

 past week include two Common Marmosets {Hapale jacclnis) 

 from South-East Brazil,'^presented by Mr. Stanley Gibson ; a 

 Canadian Beaver [Castor canadensis) from North America, pre- 

 sented by Mr. J. R. Politzer ; a Palm Squirrel {Sciurus pal- 

 »ia7-um) from India, presented by Mr. W. Tweedie ; a Green 

 Monkey {Cercopii heats callitrichus) from West Africa, presented 

 by Mrs. E. Reeves ; a Centipede, presented by Dr. C. H. 

 Eousfield ; a Rhesus Monkey {Macacus rhesus) from India, two 

 Black-headed Lemurs {Lemur brunneus) from Madagascar, two 

 Spur- winged Geese {PUctropterus gavibensis) from West Africa, 

 a Red and Yellow Macaw {Ara chloroptera) from South Ame- 

 rica, deposited ; two Black Storks {Ciconia nigra), European, 

 two Mantchurian Crossoptilons {Crosscptilon mantchurictim) 

 from Northern China, purchased; a Puma {Felis concolor), born 

 in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Observatories. — A list of the astronomical 

 observatories of the world, by George H. Boehmer, has just been 

 reprinted from the Smithsonian Report for 1886 (Government 

 Printing Office, Washington, 1889). The work is the outcome 

 of the preliminary account published by Prof. Holden, in 1879, 

 a large amount of material having since been collected by corre- 

 spondence. The various observatories are arranged under two 

 heads — (i) American, (2) foreign— an alphabetical arrangement 

 being adopted in each case. References are made to 78 Ame- 

 rican and upwards of 200 foreign observatories, including private 

 observatories. In many cases the particulars are incomplete, 

 but it is hoped that the publication will induce the directors of 

 observatories to communicate to the author any further accounts 

 and corrections which they may deem desirable. Latitudes and 

 longitudes are given in nearly every case, and also a list of past 

 and present directors. Descriptions of the more important 

 observatories and their instrumental equipments are given. 



A Spectroscopic Survey of Southern Stars.— In a 

 private letter, Mr. R. L. J. Ellery, F.R.S., writes :—" We 

 have been making a spectroscopic reconnaissance of southern 

 stars with a ' Maclean' spectroscope on our 8-inch refractor as a 

 kind of ' jackal ' list for the great reflector, with which we intend 

 to make a systematic spectroscopic survey of stars between 

 40° S. and the South Pole. I am sending to the Royal Astro- 

 nomical Society the first list of loo stars." This is a most 

 important step, and fills a gap which has been a disgrace to 

 southern science. 



The Astro-photographic Conference. — The Coviptes 

 rendtis, containing the full proceedings of the above Congress, 



which met at Paris during the past month, have not yet been re- 

 ceived. Thp following, however, are some of the points decided 

 by the Permanent Committee : — 



The centre of the plate is to be pointed not more than 5" distant 

 from the selected point in the heavens, the size of the plate to 

 be 160 millimetres square. The size of the field adopted was 

 2° square, whilst the reseau is to be 130 millimetres square, with 

 lines 5 millimetres apart. 



The amount of overlapping decided upon was 5'. Vogel has 

 undertaken the construction and verification of the reseau. The 

 distribution of the work among the co-operating Observatories 

 has been completed, and to Greenwich is allotted that from 

 Declination -1-48 to -f 40. 



Plate glass only must be used for the plates ; the chemical 

 formula, however, is left open. The sensitiveness for the Chart 

 and for the Catalogue is to be the same. Reseau to be used 

 in both series. 



A series of standard plates will be prepared by the Paris Ob- 

 servatory, and the time of expo^ure must be adjusted so as to 

 compare properly with these standards. There will be one 

 or more bureaus established for such Observatories as cannot 

 measure their own plates. 



International Congress on Celestial Photography. 

 — There was a preliminary meeting of this Congress at Meudon 

 on September 20, to consider the programme that had been 

 drawn up by the Provisional Committee. A few slight altera- 

 tions were made in the original scheme, but the details of the 

 work were not entered into. It was, however, decided that the 

 greatest latitude should be allowed in the choice of instruments, 

 and that each observer should employ that instrument to which 

 he was accustomed, having no regard to uniformity. 



In order to indicate the spectroscopic work included in the 

 programme, a change in the style of the Congress was agreed 

 to. It is henceforth to be the "International Congress on 

 Celestial Photography and Spectroscopy." 



A large detailed drawing of the Milky Way — the result of 

 five years' labour- — is now on view at the rooms of the Royal 

 Astronomical Society, Burlington House. An explanatory note 

 win be read at the next (November) meeting of the Society. 



ASTRONOMICAL PHENOMENA FOR THE 

 WEEK 1889 OCTOBER 20-26. 



/"pOR the reckoning of time the civil day, commencing at 

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



is here employed.) 



At Greenwich on October 20 



Sunrises, 6h. 3Sm. ; souths, iih. 44m. 47'5s. ; daily decrease 

 of southing, 9 ■8s. ; sets, i6h. 55m. : right asc. on meridian, 

 I3h. 41 •3m. ; decl. 10' 31' S. Sidereal Time at Sunset, 

 i8h. 52m. 



Moon (New on October 24, I4h.) rises, ih. 3m. ; souths, 

 8h. 35m. ; sets, i5h. 52m. : right asc. on meridian, 

 loh. 31 'Sm. ; decl. 13° 56' N. 



Planet. 



Mercury.. 

 Venus ... 

 Mars ... 

 Jupiter ... 

 Saturn ... 

 Uranus... 



Rises. 



h. 0;. 



5 42 

 3 46 

 2 42 



12 24 

 I 12 



6 7 



Neptune.. 18 26* 



Souths, 

 h. m. 

 II 10 . 



10 O . 

 9 18 . 



16 16 . 

 8 19 . 



11 28 . 

 2 15 . 



Sets. 



h. m. 

 16 38 

 16 14 



IS 54 

 20 8 



15 26 



16 49 

 10 4 



Right asc and declination 

 on mendian. 

 h. m. . , 



13 6-8 

 II 562 

 II 137 

 18 13-4 

 10 15 I 

 13 24-8 

 4 97 



7 iS. 

 2 4N. 

 6 26 N. 



23 30 S. 

 12 14 N. 



8 i8S. 

 19 19. N. 



* Indicates that the rising is that of the preceding evening. 



Oct. 

 20 



21 

 22 



24 

 24 



h. 

 I 



6 



6 



II 



19 



Saturn in conjunction with and 3° i' south 



of tl e Moon. 

 Mars in conjunction with and 3° 43' south 



of the Moon. 

 Venus in conjunction with and 3° 48' south 



of the Moon. 

 Mercury stationary. 

 Mercury at least distance from the Sun. 



