April 1, 1898.] 



KNOWLEDGE. 



71 



Sftcncc Kotcs. 



In the Astiriniiiiiicdl .lounidl (Nos. 285-86), Prof. 

 Barnard gives the results of a series of observations of 

 Jupiter's fifth satellite. The period of revolution is found 

 to be llh. 57m. 23-06s. " The hourly motion of the 

 satellite is 80° 11', and the velocity in its orbit about 1(J'4 

 miles a second, which is some twelve times as rapid as the 

 motion of Phobos, the inner satellite of Mars. The 

 horizontal equatorial parallax of the new satellite is 21° 61'. 

 The distance from the surface of Jupiter is about 67,000 

 miles. The satellite seems equally bright at the eastern 

 and western elongation. No amount of magnifying power 

 lias shown it other than as a stellar point. Its shadow 

 cannot be seen in transit.'' From new determinations the 

 following values were adopted for the Jovian diameters : — 

 Equatorial (Uameter 89,790 i 65 miles. 

 Polar „ 84,300 1 80 miles. 



The values given in Young's " General Astronomy " are 

 88.200 and 83,000 miles respectively. 



The determination of the period of the new satellite by 

 Prof. C. A. Young, given in our last number, was by 

 mistake printed llh. 57m. 4s. ; it should have been llh. 

 57'4m., the 4 being a decimal and equivalent to 24s., 

 ■which corresponds very exactly with Prof. Barnard's 

 determination. 



According to Mr. Harold Jacoby, " the Rutherford photo- 

 graphic measures of the stars about fi Cygni, contained in 

 the sixth volume of the Annals af the Xcir York Academi/ of 

 Srirticcs, exhibit certain discordances which can be ex- 

 plained on the hypothesis of a large parallax for p Cygni, 

 amounting lo nearly a whole second of arc. The evidence 

 cannot be regarded as conclusive, but Mr. Jacoby thinks 

 that it is sufficiently strong to make this star an object of 

 •especial interest and promise to parallax-observers." 

 Measures taken from six negatives give 097" as the 

 parallax of the star. The parallaxes of j«, and 9 Cassiopeiie, 

 also deduced from Rutherford's photographic measures, 

 are 0-275" and 0-232" respectively. 



Our knowledge of the solar corona would no doubt 

 advance more rapidly if a means could be devised of photo- 

 graphing it in ordinary daylight. Recently the matter has 

 been taken up again by M. Deslandres, of the Paris 

 Observatory, and Prof. George E. Hale. The former 

 •observer passes sunhght through two prisms having their 

 faces parallel, but with the base of one opposite the 

 refracting edge of the other. If the whole spectrum 

 formed by the first prism pass through the second the 

 sunlight is recomposed into white light ; but by placmg 

 the prisms some distance .ipart only a portion of the first 

 spectrum traverses the second prism, and a coloured 

 image of the sun is obtained. The colour of this image 

 -can be changed by rotating the first prism ; but at present 

 no region of the spectrum has been found in which the 

 light of the corona is so much greater than diffused day- 

 light as to permit the corona to be seen or its image to 

 be registered upon a photographic plate under ordinary 

 -circumstances. Prof. Hale thinks that the best results 

 will be obtained by using ultra-violet rays in future photo- 

 graphic expermients, for there is some reason to suspect 

 that the brightness of the corona with respect to the 

 surrounding sky is inversely proportional to the wave- 

 length of the light employed for the observation. Prof. 

 Hale will shortly try an instrument, similar to the spectro- 

 hehograph, which has been constructed for the express 

 purpose of photographing the corona. 



The Actonian prize of one hundred guineas, which is 

 awarded by the Committee of Managers of the Royal 

 Institution every seventh year, has been given this year to 

 Miss Agnes M. Clerke for her works on Astronomy. The 

 recipient in 1886 was Sir George Stokes for his little book 

 on " Light." 



— .-♦-. — 



A society has recently been formed for the purpose of 

 furthering the study of the MoUusca and Brachiopoda. It 

 is to be called the Malacological Society of London, and 

 its meetings are to be held monthly, at eight o'clock in the 

 evening of the second Friday in the month, at 07, Chancery 

 Lane. Dr. H. Woodward is to be the first President. 



Dr. Scott, in his latest experiments on the proportion in 

 which hydrogen combines with oxygen to form water, finds 

 that the ratio of hydrogen to oxygen is not 2 to 1, but 

 more than 2 volumes of hydrogen to 1 of oxygen. The 

 exact ratio is 2-00246 hydrogen to 1 oxygen. This result 

 has an important bearing on the determination of the 

 atomic weights of the elements, the exact value for the 

 atomic weight of hydrogen not being known with reference 

 to other elements, such as oxygen. 



Mr. Boys with his radio-micrometer can observe a 

 deflection of the instrument, which is due to a temperature 

 difference of less than one two-millionth (^nnffooo) °^ ^ 

 degree Centigrade. In one particular case the surface 

 receiving the radiant heat is a disc only 2 millimetres in 

 diameter, and when the scale is oO inches from the mirror, 

 the hand held about a yard from the instrument isroduces at 

 once a deflection of 16 centimetres, shown by the spot of 

 light thrown by the mirror on the scale. Mr. Boys also 

 calculates that the heat received by a halfpenny at 

 1500 feet from a candle flame would, if concentrated on 

 the sensitive surface, produce a readable deflection. 



Mr. J. W. Salter, writing to the Zooiogiat from Univer- 

 sity College, Aberystwith, says that on January 4th last 

 he obtained a polecat about six miles south of Aberystwith. 

 He thinks that ihere is reason to believe the species is by 

 no means extinct in Cardiganshire. 



In Nature lor February 23rd Dr. Ball gave an interesting 

 account of lion-tiger hybrids. In the next number Mr. 

 S. F. Harmer, of Cambridge, draws attention to the fact 

 that his university possesses the skeleton and stufl'ed skin 

 of an aihdt hybrid between a lion and a tigress. It was 

 about six years old, and although inferior in size to either 

 of its parents, the animal appeared to have attained its full 

 dimensions. The shape of the head resembled that of the 

 father (the lion), whilst the form of the body was more 

 similar to that of the tigress. The body was faintly striped. 

 It was a female and had neither a mane nor a tuft at the 

 end of its tail. 



The Times recently gave an account of a process by 

 which anthracite coal bricks are now being manufactured. 

 Grains of anthracite dust are forced together, partly by 

 means of a cementing compound and partly by great 

 pressure. The coal dust is mixed with the binding 

 material in the proportion of ninety-six per cent, of the 

 former to four per cent, of the latter. These coal bricks 

 are said to m;ike an excellent fuel, and to possess a very 

 high efficiency for steam-raising purposes. Should this 

 fuel be largely used for household purposes, it is to be 

 hoped that the atmosphere of our towns will be less 

 smoky. 



