358 



KNOWLEDGE & SCIENTIFIC NEWS. 



[February, igo6. 



ASTR.ONOMICAL. 



By Charles P. Butler, A.R.C.Sc. (Lond.), F.R.P.S. 



SeetsonaLl Cha.nges on the Moon's 

 S\irface. 



Profi;ssok W. H. Pickering has several times suggested that 

 he has obtained photographic evidence of real changes on the 

 lunar surface, and he has recently stated that there will shortly 

 occur a favourable opportunity for critical examination of one 

 of these supposed variable features. This is in connection with 

 the small crater Linne, and the special observations can only 

 be properly made at the time of a lunar eclipse, so that this 

 may be done on February 8 next. 



While sexeral observers have proved that the size of the 

 white area surrounding Linne is dependent on the time that 

 the sun has been shining on it, or, in other words, on the co- 

 longitude of the sun as seen from' the moon, only four, 

 Douglass, Saunder, Wirtz and Pickering have been able to 

 observe it at the time of a total eclipse. The observers in 

 question all agree that the white spot appears larger after 

 emerging from the Earth's shadow than it did before it entered 

 it. Hence it is very desirable that not only should the number 

 of observations be increased, but definite measures of the 

 extent of enlargement might be obtained if systematic arrange- 

 ments are made. 



The observation depending on the age of the moon may be 

 made without great ditficulty by comparing a pair of good 

 lunar photographs, one taken soon after first quarter, the 

 other near full moon, when the difference may amount to 

 2" or 3". In general the higher the sun the smaller is the spot. 

 The observation during total eclipse is not so simple. An 

 attempt was made during the last eclipse visible in America, 

 in October, igo2, but failed owing to lack of co-operation. If 

 observations can be secured this year, it is recommended that 

 for an hour or so, both before and after the shadow transits 

 Linne, as many micrometer measures as possible should be 

 taken, all approximately in a north and south direction, as 

 measures in this position angle are more accurate than others 

 on account of the moon's orbital motion. Owing to the hazi- 

 ness of the edge of the white spot surrounding the crater, it 

 would be advisable to start observations on a previous night 

 to become familiarised with the region. 



Rather conspicuous changes also occur in the white spots 

 near the centre of Eratosthenes during the course of a luna- 

 tion, and observers not possessing micrometers might en- 

 deavour to detect changes by comparison with neighbouring 

 features of more constant dimensions. 



Periodica.1 Comets due in 1906. 



Notice is given by Mr. W. T. Lynn of the expected return 

 of two periodical comets during the present year. 



Comd Holmes, which it is hoped we shall see during the 

 spring months, was discovered at Islington on November 6, 

 1892, in Andromeda, and was first thought to be connected 

 with the lost Biela's comet, but this was disproved when its 

 motion was determined. It appeared strange that the comet 

 was not seen about the time of its perihelion passage during 

 August, 1S92, and it has been supposed that a subsequent 

 increase of intrinsic brightness may have taken place. The 

 comet is remarkable for the small eccentricity of its orbit, 

 which lies wholly between those of Mars and Jupiter; its 

 perihelion distance from the sun is 2'2, and that of aphelion is 

 5-0. The period is about 6'8 years. It was seen on its second 

 return by Professor Perrine on June 11, iSgg, having passed 

 perihelion on April 28. Another return to perihelion will 

 therefore be due in the present year, and may possibly occur 

 in the earlier months of the year. 



Finlay's Comet, discovered at the Cape of Good Hope on 

 September 26, 1S86, passed perihelion on November 22 of 

 the same year, and with a period of about 6| years, was 

 next seen in 1893 by Mr. Finlay again on May 17, which 

 would be about a month before the calculated time of peri- 

 helion on June 16. At the return in the winter of 1899 

 the comet was unfavourably placed and escaped observation, 

 and is due during the summer months of igo6. 



Giacobini's Comet, 1905 (c). 



This comet has been frequently seen on the Continent, but 

 the unfavourable weather appears to have prevented many 

 observations in England, as it could only be seen some little 

 time before sunrise. Herr Stromgren has computed the fol- 

 lowing elementa : — 



T = 1906 Jan. 2263 G.M.T. 



u = 198° 22' 



Si = 91° 55' 



' = 43° 37' 



q = 02238 

 The following ephemeris will serve as a guide in searching 

 for the comet : — 



Recent Meteorological Determinations 

 by Kites. 



Although systematic examination of the upper atmosphere is 

 not yet carried out on this side with the completeness adopted 

 in America, where it is chiefly due to the initiative of Pro- 

 fessor Rotch, of the Blue Hill Observatory, we have constant 

 evidence of the tendency to recognise the importance of this 

 somewhat difficult branch of meteorological science. 



At a recent meeting of the Royal Meteorological Society, 

 Mr. G. C. Simpson described a series of attempts to fly kites 

 for registration purposes from the deck of a mission ship 

 (Queen Alexandra) attached to a deep-sea fishing fleet in the 

 North Sea. The work was carried out during July and 

 August, 1905, on behalf of the joint Kite Committee of the 

 Royal Meteorological Society and the British Association. 

 Eight ascents were successfully secured, and the greatest ele- 

 vation recorded was 5800 feet. 



Mr. C. J. P. Cave gave an account of his operations in Bar- 

 bados, during April and May, 1905, and from an examination 

 of the traces secured, Mr. \V. H. Dines concludes that the 

 humidity there varied from 60 per cent, at the surface of the 

 ground, rising to So-go per cent, at heights from 1000-2000 

 feet, and then gradually falling off again to 50 per cent, or less 

 as the elevation still further increases. It is noted that these 

 values are lower than would have been expected in the region 

 over a tropical ocean. 



The increase is of the normal type, but the maximum value 

 occurs at a far lower elevation than is the case in Europe. 

 Extended observations having shown that it is probable that 

 the relative humidity forms a reliable guide to the state of the 

 vcfrtical circulation, a low humidity indicating a descending 

 current of air, it may be inferred from the above observations 

 that there is a settling down of the atmosphere over the 

 regions of the smaller West Indian Islands during April and 

 May. 



We believe that experiments are also in progress by the 

 Indian Meteorological Department for exploring the upper 

 atmosphere by means of automatic instruments attached to 

 kites, and if successful it is expected to derive much practical 

 information which should be extremely useful in increasing the 

 accuracy of the weather forecasts so necessary to the welfare 

 of the industries of the country. 



Intrinsic Intensity of the Solar Corona.. 



Observing at Burgos on August 30, 1905, M. Charles 

 Fabry determined the intrinsic intensity of various portions of 



