l82 



NA TURE 



[June 



The Oxford Univk;rsity Observatory. — The twenty- 

 third annual report of the visitors of the University Observ- 

 atory appears in a recent number (June 14) of the Oxford 

 University Gazette. The report refers to the period from June 

 I, 1897, to May 31, 1898, and exhibits the state of the observ- 

 atory on the last-named day. One of the main points referred 

 to by Prof. Turner in the report, is that of the necessity of com- 

 pleting the observatory by attaching to it a residence. This, 

 he points out, is urgent, since it is most imperative that the 

 official staff" should be as near their work as possible when both 

 routine observational work and students have to be dealt with. 

 Prof. Turner refers to a very curious accident that occurred to 

 the level belonging to the Barclay transit circle that is used for 

 time determinations, which is well worth repeating.. "The 

 striding level, weighing 19 lbs., which was suspended over the 

 instrument by means of a cord, pulley and counterpoise, fell 

 (from its usual position when not in use near the roof) a distance 

 of three or four feet on to the instrument, owing to the snap- 

 ping of the cord. It w^as found the next morning standing 

 upright, with its feet on the pivot covers as if in position for 

 an observation. The blow had thus been received by the pivot 

 covers, and no other part of the instrument had apparently been 

 damaged or even struck. The brass tube of the level itself was 

 shattered, but the glass-tube inside was not broken !" Surely 

 this is quite a unique accident ? 



The measurement and reduction of the plates for the Astro- 

 graphic Catalogue seem to be proceeding apace, an average of 

 3951 measures of the star positions and magnitudes being made 

 every week, the total number for the year being 205,443. The 

 main result of the year's work is that the prospects of achieving 

 the object aimed at are brighter than previously : this was, as 

 Prof. Turner states, that by the middle of icoi we may be ready 

 to furnish, or demand, the positions and magnitudes of the 

 brighter stars in zones + 24° to + 32° to the number of some- 

 thing like a quarter of a million. The speed at which these 

 measures can be made, can be gathered from the statement that 

 " whereas at first thirty or forty star-measures an hour was 

 thought fair work, the more skilful can now measure 150 

 per hour or more." The new photographic transit circle 

 has involved much experimental work, and is proceeding 

 satisfactorily. 



The Supposed Variable Y Aquil-k. — In the series of 

 measures to determine the light curves of variable stars of short 

 period north of -40° Declination with the meridian photometer, 

 the curve of the star -f 10° 3787 was not found to be smooth. 

 This star had previously been catalogued by Chandler as vary- 

 ing from 5 '3 to 57 in a period of 4-986 days. It was also 

 suspected by Gould, confirmed by Chandler 1894, and also by 

 Yendell. Mr. Wendell has recently made some observations 

 (Harvard College Observatory Circular, No. 30) with the photo- 

 meter attached to the 15-inch equatorial telescope, on six nights 

 in May last, eighty sittings being made each night, the com- 

 parison star employed being + 10° 3784. The mean of the 

 differences of magnitude showed very little variation, and, as 

 Prof. Pickering states, fails to show any evidence of variation, 

 since deviations of a tenth of a magnitude may be ascribed to 

 errors of observation. Since it is " impossible to prove that the 

 light of a star never changes, this star may still be an Algol 

 variable with a short time of variation, or the period may be 

 entirely wrong." 



COMPANIONS OF ARGON} 



T^OR many months past we have been engaged in preparing 

 •^ a large quantity of argon from atmospheric air by absorb- 

 g the oxygen with red-hot copper, and the nitrogen with 

 magnesium. The amount we have at our disposal is some 18 

 litres. It will be remembered that one of us, in conjunction 

 with Dr. Norman Collie, attempted to separate argon into light 

 and heavy portions by means of diffusion, and, although there was 

 a slight difference ^ in density between the light and the heavy 

 portions, yet we thought the difference too slight to warrant the 

 conclusion that argon is a composite substance. But our 

 experience with helium taught us that it is a matter of the 



1 "On the Companions of Argon." By William Ramsay, F.R.S., and 

 Morris W. Travers. Paper read at the Royal Society, June 16. 



2 Density of lighter portion, I9'g3 ; of heavier portion, 2o'oi (Roy. Soc. 

 Proc, vol. 60, p. 206). 



NO. 



1495, VOL. 58] 



greatest difficulty to 'separate a very small portion of a heavy 

 gas from a large admixture of a light gas ; and it therefore 

 appeared advisable to re-investigate argon, with the view of 

 ascertaining whether it is indeed complex. 



In the meantime. Dr. Hamp.son had placed at our disposal his 

 resources for preparing large quantities of liquid air, and it was a 

 simple matter to liquefy the argon which we had obtained by 

 causing the liquid air to boil under reduced pressure. By means 

 of a two-way stopcock the argon was allowed to enter a small 

 bulb, cooled by liquid air, after passing through purifying re- 

 agents. The two-way stopcock was connected with mercury 

 gas-holders, as well as with a Topler pump, by means of which 

 any part of the apparatus could be thoroughly exhausted. The 

 argon separated as a liquid, but at the same time a considerable 

 quantity of solid was observed to separate, partially round the 

 sides of the tube, and partially below the surface of the liquid. 

 After about 13 or 14 litres of the argon had been condensed, the 

 stopcock was closed, and the temperature was kept low for .some 

 minutes in order to establish a condition of equilibrium between 

 the liquid and vapour. In the meantime the connecting tubes 

 were exhausted, and two fractions of gas were taken off by lower- 

 ing the mercury reservoirs, each fraction consisting of about 50 

 or 60 cubic cm. These fractions should contain the light gas. 

 In a previous experiment of the same kind a small fraction of 

 the light gas had been separated, and was found to have the 

 density 17 '2. The pressure of the air was now allowed to 

 rise, and the argon distilled away into a separate gas-holder. 

 The white solid which had condensed in the upper portion of 

 the bulb did not appear to evaporate quickly, and that portion 

 which had separated in the liquid did not perceptibly diminish 

 in amount. Towards the end, when almost all the air had 

 boiled away, the last portions of the liquid evaporated slowly, 

 and when the remaining liquid was only sufficient to cover the 

 solid, the bulb was placed in connection with the Topler 

 pump, and the exhaustion continued until the liquid had 

 entirely disappeared. Only the solid now remained, and the 

 pressure of the gas in the apparatus was only a few millimetres. 

 The bulb was now placed in connection with mercury gas- 

 holders, and the reservoirs were lowered. The solid volatilised 

 very slowly, and was collected in two fractions, each of about 

 70 or 80 cubic cm. Before the second fraction had been taken 

 off, the air had entirely volatilised, and the jacketing tube 

 had been removed. After about a minute, on removing the 

 coating of snow with the finger, the solid was seen to melt, 

 and volatilise into the gas-holder. 



The first fraction of gas was mixed with oxygen, and sparked 

 over soda. After removal of the oxygen with phosphorus it 

 was introduced into a vacuum-tube, and the spectrum examined. 

 It was characterised by a number of bright red lines, among 

 which one was particularly brilliant, and a brilliant yellow line, 

 while the green and the blue lines were numerous, but com- 

 paratively inconspicuous. The wave-length of the yellow line, 

 measured by Mr. Baly, was 5849*6, with a second -order grating 

 spectrum. It is, therefore, not identical with those of sodium, 

 helium, or krypton, all of which equal it in intensity. The wave- 

 lengths of these lines are as follows : — 



Na(D,) 

 Na (D.,) 

 He (D3) 

 Kr (DJ 

 Ne (D5) 



5895 ■» 

 5889-0 



5875-9 

 5866-5 

 58496 



The density of this gas, which we propose to name "neon"' 

 (new), was next determined. A bulb of 32-35 cubic cm. 

 capacity was filled with this sample of neon at 612-4 mm. presr 

 sure, and at a temperature of 19-92° it weighed o 03 184 gram. 



Density of neon 



14-67 



This number approaches to what we had hoped to obtain. 

 In order to bring neon into its position in the periodic table, a 

 density of 10 or li is required. Assuming the density of argon 

 to be 20, and that of pure neon 10, the sample contains 53-3 

 per cent, of the new gas. If the density of neon be taken as 1 1, 

 there is 59-2 per cent, present in the sample. The fact that the 

 density has decreased from 17-2 to 14-7 shows that there is a 

 considerable likelihood that the gas can be further purified by 

 fractionation,^ 



1 June 21. — After a preliminary fractionation, the density has been still 

 further reduced to 13-7. 



