374 



NATURE 



[February 17, 1898 



or Amber as a Gem," has /been published by Messrs. Sampson 

 Low, Marston and Co., Ltd. The volume brings together 

 many facts of interest concerning the origin and decorative uses 

 of amber. 



The determination of the density of a gas has, till compara- 

 tively recently, been regarded as an operation of great diffi- 

 culty, requiring elaborate apparatus and a large quantity of 

 material. In the course of his researches on argon and helium, 

 however. Prof. Ramsay has shown that it is possible by direct 

 weighing to arrive at a reasonably accurate result upon as small 

 a quantity as thirty cubic centimetres. In two recent numbers 

 of the Comptes rendus are two contributions to this subject 

 by M. Th. Schloesing-, jun., in which he gives a most ingenious 

 method of measuring the density of a gas, based upon the 

 balancing of two columns of the gases in a U-tube. Two 

 vertical tubes about one metre in length communicate at their 

 lower ends by a three-way tap ; in one is placed an easily 

 absorbable gas of known density, such as carbon dioxide, and 

 in the other the gas under examination. On allowing the 

 columns to communicate through the tap, a state of equilibrium 

 between the gas, carbon dioxide, and air is set up after about 

 four minutes, and the level of the invisible surfaces of separa- 

 tion then determined by absorbing the carbon dioxide with 

 potash. In order to reduce the unavoidable diffusion of the 

 gases, very narrow tubes were taken (i'6 mm. to 27 mm. in 

 diameter), with the resulting advantage of reducing the quantity 

 necessary for a determination. In the second paper data are 

 given for nitrogen, oxygen, and methane, from which it would 

 appear that an accuracy of i/i<xx5 is obtainable upon five to 

 seven cubic centimetres of gas. With hydrogen only was there 

 ,2l failure, the mutual diffusion of the two gases being too rapid 

 to allow of equilibrium being set up. There can be no doubt 

 "that the method will admit of many useful applications. 



The additions to the Zoological Society's Gardens during the 

 past week include a Green Monkey (Cercopilhecus callitrichtis) 

 from West Africa, presented by Mr. Robert O'Callaghan ; a 

 Horned Lizard {Pkiynosotna cornutum) from California, pre- 

 sented by Mr. Charles Iseard ; three Shaw's Gerbilles (6^dr- 

 Mllus shawi), born in the Gardens. 



OUR AS TRONOMICAL COL UMN. 



A Probable New Star. — In Circular No. 45 from the 

 Wolsingham Observatory, dated February 14, the Rev, T. E. 

 Espin states that an eighth-magnitude red star not in B.D. was 

 found the previous night, its place being R.A. 7h. 12m. i6s., 

 Decl, + 32° 19' (1855). 



New Photographs of Nebul/e. — With a reflector having 

 the extraordinary ratio of i metre aperture to 3 metres focal 

 length, M. A. Rabourdin has taken some remarkable photo- 

 graphs of several nebulse at the Meudon Observatory, and he 

 gives a detailed account of them in Comptes rendus for January 

 31, On the ring nebula in Lyra he made three ex- 

 posures — of twenty, thirty-five and fifty-five minutes. "These 

 three plates," he remarks, "show that for this annular nebula 

 the nebulosity of the interior increases with the time of ex- 

 posure, whilst the total diameter increases very little. The final 

 result is an elliptical nebula in place of the annular one taken 

 with the short exposure. The photographs also show very 

 plainly a star at the centre of the ring, which is, moreover, 

 visible to the eye in the telescope ; but neither the drawings of 

 Herschel in 1833, Lord Rosse in 1844, nor that of Trouvelot in 

 1873, give any indication of it. Hence this would tend to show 

 a comparatively recent change." 



With an exposure of fifty minutes on the planetary nebula in 

 Aquarius, a photograph was obtained showing two protuberances 

 diametrically opposite, which would lead one to suppose that the 

 central globe is surrounded by a diffuse belt analogous to 

 Saturn's ring. 



A photograph of the nebu'a in Andromeda, with only one 



NO. 1477, VOL. 57] 



hour exposure, is said to exhibit as much detail as those pre- 

 viously obtained with four times the exposure ; and the 

 nebula is so extensive, that it was quite impossible to photo- 

 graph the whole region on one single plate. 



A photograph of the nebula in Triangula shows that it is a 

 beautiful spiral one. 



The region of the Pleiades was also photographed, giving one 

 hour exposure, with Alcyone in the centre of the plate. Even 

 with this comparatively short exposure, MM. Henry have dis- 

 covered nebula absolutely invisible in the telescope, enriching 

 this region still more with two other new nebulae surrounding 

 Atlas and Pleione. This photograph also shows more than the 

 beautiful chart of the Pleiadies taken by MM. Henry, and exhibits 

 additional streams of nebulous matter which apparently bind 

 together certain stars of this group. 



Carbon in the Chromosphere, — That carbon existed in 

 the solar spectrum itself was at one time a matter of doubt, but its 

 existence was established long ago by the early researches of Sir 

 Norman Lockyer. Now, with the aid of the 40-inch telescope oi 

 the Yerkes Observatory, Prof. Hak has observed the presence 

 of carbon in the chromosphere, and his paper on this subject is 

 to be found in the December number of the Astrophjrsicat 

 Journal. The observations were made last September, and the 

 green fluting near b was distinctly seen as a bright reversal in 

 the chromosphere. M. Deslandres, wha was visiting the ob- 

 servatory at the time, bad no difficulty in seeing the lines, and 

 they have since been observed by Profs. Rui^e and Keeler. 



These results are interesting, in the light of the fact that the 

 photographs of the total eclipse of 1896 show a decided infiueiKe 

 of the prominences on the corona, and the examination of the 

 corona itself at the last eclipse, for the presence of carbon might 

 possibly have led to fruitful results. 



Parallax of Sirius. — In the Monthly Notices for January, 

 Dr. Gill discusses a series of observations for the parallax of 

 Sirius, made by him in 1888-89 with the Cape heliometer. The 

 comparison stars used were both of 87 magnitude ; one, which 

 he denotes by 7, being 4310" distant, and the other, 5, 4536" 

 away from Sirius, with respective position angles of 279°*i7 and 



IOI°"26. 



From these observations he deduces a value of o"'370 + 

 o"'0097, which is in remarkably close agreement with his 

 well-known result of o"'370 ± o''009 from his 1881-83 

 observations. 



Dr. Gill states that by this method of measurement it was 

 possible to determine parallaxes so small as 1/50 of a second 

 with .some confidence — a degree of accuracy not previously at- 

 tained in astronomical researches of any kind. He therefore 

 thinks we may regard the parallax of Sirius as now satisfactorily 

 determined, and that the corrections depending on a parallax of 

 o"*37 might with advantage be introduced in the apparent 

 places of Sirius given in the national ephemerides. 



We note with pleasure that Mr. A. C. D. Crommelin, in the 

 Monthly Notices for January, continues his paper which ap- 

 peared in the December number, on the " Ephemeris for physical 

 observations of Jupiter, 1898." We had been so long accus- 

 tomed to seeing the late Dr. Marth's name attached to these 

 and similar tables for the moon and other planets, that it was 

 doubtful who would volunteer to fill his place ; but we are glad 

 to find that one so able as Mr. Crommelin has undertaken this 

 task. 



THE ATOMIC WEIGHTS OF NICKEL AND 

 COBALT 



T^HE determination of the atomic weights of nickel and 

 cobalt has attracted a considerable amount of attention 

 during the last few years, the numbers obtained by different 

 workers exhibiting relatively startling variations. Thus, including 

 only the four most recent results, the values for cobalt vary 

 between 5878 (Hempel and Thiele, 1895) and 60-12 (Schiitzen- 

 berger, 1892). Similar variations observed for nickel by Kruss, 

 led him to the conclusion that this metal contained a new 

 element, to which he gave the name of "gnomium"; but 

 recent work has not tended to confirm this view. In the 

 Proceedings of the American Academy of Arts and Sciences 

 for November and December last, are two important con- 

 tributions to this subject, by Richards and Cushman and 



