138 



NA TURE 



[July 29, 1909 



help of the Snow telescope at Mount Wilson, California, 

 at an altitude of 1760 metres, Dr. Hale shows that sun- 

 spots consist of columns of ionised vapours circulating in 

 opposite directions in the two solar hemispheres, the axis 

 of rotation being, in general, inclined at a considerable 

 angle to the normal to the solar surface. There appears 

 to be evidence of connection beneath the solar surface of 

 the vortices observed north of the solar equator with those 

 south of that line. The whole of the observations afford 

 strong support to the theory that sun-spots are the normal 

 products of the convection currents which occur in the sun. 

 The Bulletin international for 1907 of the Bohemian 

 socictv, L'.\cadi5mie des Sciences de TEmpereur Francois 

 Joseph I., was published in 1908, and a copy has just 

 reached us. Drs. B. Kucera and B. Masek write in 

 English on the radiation of radio-tellurium, and continue 

 a description of their researches, which have led them 

 to the following conclusions among others. The absorp- 

 tion of the o rays from radio-tellurium in metals and 

 gases investigated by Bragg 's method is manifested 

 similarly as with o rays of radium and its first trans- 

 formation products by lowering of the ionisation curve. 

 The atomic stopping power is very nearly proportional to 

 the square root of the atomic weight, and possesses almost 

 the same values as Bragg found for radium C. It is 

 probable, though, that the proportionality constant in- 

 creases slightly with atomic weight. For the same gas 

 (air) the ranges corresponding to the a rays of the same 

 velocity are inversely proportional to the pressure (density) 

 of the gas. The ranges for the rays of the same velocity 

 in different gases (air, oxygen, carbon dioxide) are in- 

 verselv proportional to the mean square roots of their 

 atomic weights. The existence of a secondary radiation 

 of o rays which ionises air at ordinary pressure cannot 

 be taken as ascertained. 



From the account, published in Engineering for July 16, 

 of the trials conducted recently by the Scottish Automobile 

 Club, it is evident that electric ignition can be made 

 perfectly trustworthy if well carried out. Fifty-eight cars 

 were fitted with high-tension magnets, four used accumu- 

 lators only, and three low-tension magnets. Only one car 

 fitted with high-tension magnets had any stops at all, 

 except for cleaning or changing sparking-plugs, a matter 

 which often depends more on the lubrication than on the 

 ignition apparatus. Of the other systems, there was only 

 one small stoppage in any of the cars having accumulator 

 ig[\ition, and two considerable stops in cars fitted with 

 low-tension magnets. The Albion car, fitted with low- 

 tension magnets, went through without an ignition stop, 

 as it has done on previous occasions, and it may be 

 taken for granted that the low-tension system, like the 

 high-tension, can give completely satisfactory results. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in August: — 

 Aug. 3. 23h. Mercury in superior conjunction wiih the Sun. 



5. 4(1. 15m. Mars in conjunction with the Moon (Mars 



o°i3'S.). 

 „ 23h. Saturn stationary. 



6. 9h. 45m. Saturn in conjunction with the Moon 



(Saturn 1° 32' N.). 

 10-12. Perseid maximum, 



II. igh. 2m. Venus in conjunction with Jupiter (Venus 



o' 12' N.). 

 13. Sh. Mars in perihelion. 

 17. Ilh. 36m. Jupiter in conjunction with the Moon 



(Jupiter 4° 17' S.). 

 iS. oh. 13m. Venus in conjunction wilh the Moon 



(Venus 4° 15' S.). 

 23. 3h. Mars stationary. 



NO. 2074, VOL. 81] 



.\ Large Group of Sun-spots. — During the past week a 

 group of sun-spots, of abnormal size for this period of 

 the sun-spot cycle, has been visible on the solar disc — even 

 to the naked eye. This large group has developed from 

 a few scattered,' small nuclei which came round the eastern 

 limb on July 18, and now includes a leading sjxjt of large 

 dimensions and two separate trails of smaller spots. In 

 addition to the large group there was another, preceding, 

 group of medium size and two smaller ones to be seen on 

 the disc on Saturday last. This outburst still further 

 emphasises the extension, in time, of the sun-spot ma.xi- 

 mum of 1905-6. 



Physical Interpretation of Lunar Features. — In pre- 

 senting the eleventh fascicle of his photographic map of 

 the moon, M. Puiseux placed before the Paris .Academy of 

 Sciences some ideas as to the nature and history of the 

 lunar landscape, suggested by the study of the photo- 

 graphs. From the absence of any appearance of division 

 into parallels of the dark and light areas, M. Puiseux 

 argues that the moon certainly has not polar regions of 

 ice and snow such as those seen on the earth and Mars. 

 Then, considering the probable presence or absence of 

 water, it follows that the moon's surface must either be 

 glaciated completely or shows no trace of water areas. 



.Against the former suggestion, which, it will be remem- 

 bered,' is the one upheld by Herr Fauth, the noted 

 selenologist, there is the relatively low albedo, comparable 

 to that of the terrestrial volcanic and siliceous rocks, but 

 certainly much less than that of snow or ice, and there is 

 also the fact that extremely bright and extremely dark 

 areas are mixed up indiscriminately in small areas. M. 

 Puiseu.x promises a further communication dealing with 

 the subject of the form and distribution of the dark lunar 

 spots seen on the same photographs (Comptes rendus, 

 No. 26). 



Double-star Measures. — No. 158 of the Lick Observa- 

 tory Bulletins contains the fourteenth list of double stars 

 discovered and measured by Prof. R. G. Aitken with the 

 36-inch refractor of the Liclc Observatory. All the pairs 

 measured are separated by distances of less than 5", and 

 in eighty-two cases less than 2". The present publication 

 contains the measures of 100 double stars, and brings the 

 total number discovered by Prof. Aitken to 2000, 74 per 

 cent, of which are separated by distances of less than 2". 



A discussion of the available data of 7500 known pairs 

 leads Prof. Aitken to the conclusion that, among the stars 

 down to the ninth magnitude, the number of doubles 

 having separations of less than 2" is greater than those 

 separated by distances exceeding 2", but less than 5", in 

 the proportion of 3/1. Hence follows a strong confirma- 

 tion of the probability that practically all the closer doubles 

 are in reality binary systems, not merely optica! pairs. 



No. 4338 of the Astrononiische Nachrichten contains the 

 measures of a number of double stars made by Mr. E. D. 

 Roe, jun., with the 6J-inch refractor of his observatory 

 at Syracuse. 



Maximum of Mira in 190S. — Observations of the bright- 

 ness of o Ceti were made by M. Luizet, at St. Genis-Laval, 

 between September 18 and November 28, 1908, and show 

 that the maximum brightness, 3-6 mag., occurred on 

 October 12 ; this agrees within one day with the epoch 

 given in the .4Hiiiiai>c dii Bureau dcs Longitudes (Astro- 

 noniische Xachricliten, No. 4340, p. 332, July 16). 



Observations of Jupiter's Fifth S.'vtellite. — .Although 

 finding it a difficult object to measure. Prof. Barnard 

 succeeded in obtaining measures of Jupiter's fifth satellite 

 during 1908 and 1909 suflficient to determine the times 

 of, and distances at, elongation, and to give a new value 

 of the satellite's period. Western elongations took place 

 at 1909 February 21 I4h. 25-4m. (central standard time) 

 and 1909 March 14 I2h. 2q-6m., and the apparent 

 distances were 56-47" and 56-00" respcctivelv : taking 

 A = 5-20, the latter become 48-08" and 47-03". 'Combining 

 these values with those determined in 1892, the period 

 becomes o-498i79o6d., which agrees within one-thousandth 

 of a second of time with that previously determined. It 

 therefore appears that the period is now quite accurately 

 known, and has suffered no sensible change during the 

 seventeen vears that the satellite has been under observa- 

 tion (Astronomische Nachrichten, No. 4339)- 



