August 30, 1906] 



NA TURE 



453 



A second telegram from the same source states that the 

 comet was observed at Hamburg by Herr Graff on 

 August 23, its position at I3h. ii-3m. (Hamburg M.T.) 

 being R.A.=22h. 48m. 53-Ss., dec. = + io° 21' 7'. 



From this it is seen that the comet is apparently in the 

 constellation Pegasus, a little to the north of a Pegasi, 

 and is moving in a south-westerly direction. This position 

 crosses our meridian at about 12 o'clock midnight 



Imnlav's Comet (1906^). — This comet will arrive at its 

 perihelion, according to M. Schulhof's elements, on 

 September 7'S. 



As shown by the following extract from the ephemeris 

 published in No. 4109 of the AsUonomische Nachrichten, 

 the comet is now apparently travelling through the extreme 

 niireh-eastern corner of Orion towards Gemini, which it 

 will enter on September g. On September 7 it will pass 

 about 1° south of 71 Orionis, and on September 13 about 

 2° 3(1' north of 7 Geminorum. On the latter date the 

 comet will rise about five hours before sunrise, i.e. about 

 12-30 a.m. 



Ephemeris 12/1. (Paris M.T.). 



Sept. 9 



a (app.) 5 (app.) 



6 17 

 6 25 

 633 

 6 40 



+ 18 27 

 + 18 47 

 + 19 4 

 + 19 19 



Greenwich Sun-spot Numbers. — An innovation which 

 is likely to be found a great convenience by everyone who 

 has to discuss sun-spot observations appears in the August 

 number of the Observatory. 



Up to the present such workers have had to wait until 

 about the middle of the next year before the serial numbers 

 allotted to the sun-spots of any one year by the Greenwich 

 authorities became available for general use. Now, with 

 the sanction of the Astronomer Royal, Mr. Maunder pro- 

 poses to publish these numbers month by month. 



The first instalment, giving the numbers for the quarter 

 January-March, igo6, appears in the current Observatory. 

 Next month's issue will contain the data for the second 

 quarter, and after that each month will be given separately, 

 so that the numbers for July will appear in October, and 

 so on. 



Other data, e.g. the duration and the latitude and longi- 

 tude of each spot-group, are also given, but, as they are 

 determined from simply a preliminary examination, these 

 are not to be accepted as final values. 



The Origin of the Zodi.acal Light. — Some interesting 

 observational results, and deductions therefrom regarding 

 the origin of the zodiacal light, appear in a brochure 

 written by Mr. Maxwell Hall, of Montego Bay, Jamaica, 

 and issued as a reprint from the Monthly Weather Review 

 for March, 1906. 



Mr. Hall's observations were made at Jamaica in 1899 

 and iqoi, and determined the breadth of the light and its 

 boundaries at different distances from the sun. On re- 

 ducing the observed latitudes according to their longi- 

 tudes, or distances from the first point of Aries, Mr. Hall 

 obtained striking evidence which tends to show that the 

 light is parallel to the invariable plane of the solar system, 

 evidence which was apparently confirmed by the results 

 obtained by other observers. 



On these grounds Mr. Hall arrives at the conclusion 

 that the zodiacal light is caused by the reflection of sun- 

 light from masses of meteoric matter still contained in 

 the invariable plane, which mav be considered as the 

 original plane, of the solar system. 



If this conclusion is correct, and the phenomenon is 

 astronomical in its origin, the light should be seen better 

 and more frequently from observing stations situated in 

 high altitudes, and the editor of the Review especially 

 commends its observation to workers located at such 

 stations. 



.A Modified Form of Sol.ar Eye-piece. — From Prof. 

 Ccraski, of Moscow, we have received a brief description 

 of a solar eye-piece which he is using, and has found to 

 be most effective, for the detailed study of sun-spots. This 



NO. 1922, VOL. 74] 



eye-piece is analogous to one described by Dawes in vol. 

 xxi. of the Memoirs of the Royal Astronomical Society, 

 but as no one seems to have used this for the study of 

 minute details in sun-spots, Prof. Ceraski describes the 

 one he is now using. 



The apparatus is furnished with a positive eye-piece and 

 a copper plate pierced with circular apertures of various 

 diameters, thus forming an adjustable diaphragm. This 

 copper plate is protected by a disc of asbestos which con- 

 tains a central aperture slightly larger than the largest in 

 the diaphragm. The dark glass is a combination of black 

 mica and blue glass. 



Using this eye-piece with the full aperture of the Pulkowa 

 iS-inch refractor, Prof. Ceraski was surprised at the amount 

 of detail seen. 



PHYSICS AT THE BRITISH ASSOCIATION. 



'X'HE proceedings of the Mathematical and Physical 

 Section (A) commenced on Thursday, August 2, with 

 the delivery of the presidential address by Principal E. H. 

 Griffiths, F.R.S. This address has already appeared in 

 full in these columns (August 9, p. 356). 



The chief interest of the meetings in this section 

 arose in connection with several discussions which were 

 arranged and taken up with avidity. On August 2 

 the Earl of Berkeley described his experiments on the 

 measurement of osmotic pressure, both directly and 

 indirectly from measurements of vapour pressure. The 

 two methods give results agreeing to within 5 per cent. 

 Mr. W. C. D. Whetham followed, and treated the same 

 subject from the standpoint of thermodynamics and the 

 dissociation theory, thereby stimulating Prof. Armstrong 

 to make a vigorous attack on everything connected with 

 thermodynamics and dissociation. In Prof. Armstrong's 

 opinion the secret of osmotic pressure is to be sought in 

 a thirst of complexes of water molecules. He laid stress 

 on the importance of recent work in America, which 

 proved that Boyle's law was satisfied for much greater 

 strengths of solution than was shown by Lord Berkeley's 

 results. In the course of discussion it seemed, however, 

 that the difference was rather one of interpretation of results 

 than of the experimental results themselves. Mr. 

 Whetham, in his rejoinder, declared also in favour of a 

 " thirst " hypothesis, but differed in regard to the 

 mechanism of it. 



On Friday, August 3, two important discussions took 

 place. The former was opened by Mr. Frederick Soddy, 

 the subject being the evolution of the elements. Mr. 

 Soddy outlined the subject from the earliest times to the 

 most recent developments in connection with radio-active 

 changes. Uranium gradually changes to radium, radium 

 to its emanation and several other successive products, until 

 in all probability it becomes lead. Lead in turn suffers 

 a gradual transmutation into silver. These changes pro- 

 ceed spontaneously, setting free energy as they occur. 

 With regard to active attempts at transmutation in the 

 reverse direction, which, of course, require a correspond- 

 ingly large supply of energy, Mr. Soddy considers that 

 success will be found first in a nearly complete vacuum 

 carrying an electric discharge. Here there is very little 

 matter carrying a large amount of energy, so that the 

 necessary conditions would seem to be supplied. The 

 Hon. R. J. Strutt laid stress on the fact that in radio- 

 active changes helium was the only non-valent element 

 produced, while in our atmosphere argon was largely pre- 

 ponderant. Had argon been formed bv other transmuta- 

 tions? Dr. O. W." Richardson and Dr. H. A. Wilson 

 discussed the apparent disappearance of matter in vacuum 

 tubes, alluding to quantitative experiments made in the 

 Cavendish Laboratory. Prof. Schuster emphasised the 

 nearly complete indifference of radio-activity to tempera- 

 ture changes, the only temperature effect yet discovered 

 being a small one found by Mr. W. Makower working in 

 his laboratory. He had experiments in progress on the 

 influence of high pressures with the aid of apparatus de- 

 signed by Mr. Petavel. With this apparatus a pressure 

 of 2000 atmospheres can be obtained; no change in radio- 

 active charge brought about thereby had yet been detected. 



