266 Chronicles of Science. [April, 



Proceedings of the Koyal Astronomical Society. 



Some very careful observations on radiant points of shooting-stars 

 were communicated to this society at the meeting on December 9th, 

 by Mr. A. S. Herschel. This subject is one which this observer has 

 made peculiarly his own, and the mass of facts which is being care- 

 fully collected and collated by such observers cannot fail to bear 

 valuable fruit at no very distant time. The present paper, consisting 

 as it does principally of diagrams and tabulary matter, defies conden- 

 sation, but we may state that they appear to lead to the conclusion 

 that the length in miles of the luminous excursions of meteors depends 

 not so much upon the mass of a meteor as upon the depth of the 

 inflaming atmospheric stratum through which it has to pass, and that 

 this in general is the same for all meteors. The author likewise sup- 

 poses that there are two meteoric orbits, neither of whose semi-axes 

 major differ more than a fourth part from radii vectores of the earth. 

 This supposition agrees with the evidence adduced elsewhere, by Pro- 

 fessors Newton, Erman, and others, to show that the August and 

 November rings of meteors very nearly coincide in their dimensions 

 with the orbit of the earth. It adds fresh support to the conclusion 

 that meteoric orbits approach in general very nearly to the circular 

 form, but offers no explanation of their frequent retrograde motions 

 and large obliquities to the ecliptic. 



Professor Anwers has communicated the results of his researches 

 relative to the orbit of Sirius, and has deduced, by a new computation, 

 in most cases from the original sources, the following most probable 

 values of the elements from 214 equations of condition ; comprising, 

 with trifling exceptions, the whole accessible material of observations, 

 which prove to be trustworthy. 



Passage through lower Apsis . . . =1793-890 years. 



Mean yearly motion .... =7°28475 



Time of revolution .... =49*418 years. 



Eccentricity = 0-6010 



In our Chronicles we have given some observations by M. Cha- 

 cornac on the apparent diameter of Sirius. This note formed the 

 subject of a few remarks by Mr. Pritchard, the Honorary Secretary of 

 the Society, at their December meeting. He commenced by saying 

 that although the meaning of the author's term, lunette prisrnatique, 

 was somewhat doubtful, it seemed to refer to what in England would 

 be called a double-image prismatic micrometer eyepiece. The image 

 of a star formed by a lens with a circular aperture is well known to 

 be a " spurious disc," surrounded by a few coloured rings, the cause 

 being the interference of the waves of light which have passed through 

 the object-glass. The intensity of the light in the spurious disc 

 diminishes from the centre to the circumference, where it is a mini- 

 mum ; the light then varies again in intensity through a succession of 

 maxima and minima thus furnishing the rings. Suppose, then, two 

 images of the spurious disc to be formed by means of the " rotary 

 prisms " referred to by M. Chacornac, and which leave the ordinary 



