1870.] Astronomy. 391 



research into the physical habitudes of the orbs which people the 

 celestial depths. 



Professor Kirkwood's ingenious hypothesis that the periodicity 

 of the solar spots may be referred to the existence of solar regions 

 favourable to the development of spots, has received its death-blow 

 at the hands of Sir John Herschel. Our veteran astronomer is 

 still ready to devote his great powers to the study of such ques- 

 tions. In tins case he has been at the pains to mark down the exact 

 place on the sun's globe of all the spots observed by Carrington. 

 He finds no trace of a region where sun-spots occur with unusual 

 frequency, or if there are traces of such a region they are so 

 slight as to afford no sufficient foundation for Professor Kirkwood's 

 hypothesis. 



Professor Kirkwood's detection of the law that comets of small 

 perihelion distance have their perihelia nearly in the direction towards 

 which the sun is travelling, has been followed up by a careful in- 

 vestigation of the periods of some of the meteoric rings. The 

 April shower, though less familiarly recognized than the November 

 and August showers, is yet too well marked not to be admitted 

 among the periodical meteoric systems. Professor Kirkwood shows 

 that this system cannot be associated, as Weiss suggested, with the 

 first comet of 1861 ; but by comparing the dates on which remark- 

 able showers of meteors belonging to this system have appeared, he 

 exhibits the probability that the system has a period of 28J years, 

 and an aphelion distance very nearly equal to the mean distance of 

 Uranus. Dealing with the meteors of December 11-13, he finds for 

 them a period of 29^ years. For the meteors of October 15-21, he 

 obtains a period of 27J years. He adds, " if these periods are cor- 

 rect, it is a remarkable coincidence that the aphelion distances of 

 the meteoric rings of April 18-20, October 15-21, November 14, 

 and December 11-13, as well as those of the comets, I. 1866 and 

 I. 1867, are nearly all equal to the mean distance of Uranus." As 

 Jupiter has his family of dependent comets, so distant Uranus has 

 depending from his orbit a family of meteoric and cometic systems. 

 Can we suppose that those among these meteor-systems which inter- 

 sect the orbit of the earth are all which thus depend on Uranus, or 

 that they form a thousandth or even a millionth part of his family 

 of meteor-systems ? The laws of probability are enormously against 

 such a supposition ; and if it be indeed true (as we seem forced to 

 admit) that around the orbits of the major planets there cling these 

 myriads of meteoric and cometic systems, we obtain a new insight, 

 indeed, into the characteristics of the solar system. 



Saturn will continue to be favourably visible during the ensuing 

 quarter. Mars, Venus, and Jupiter will be unfavourably situated. 

 We remind our readers to look out for shooting-stars on the nights 

 of August 9-13. 



