BRITISH SCIENTIFIC ASSOCIATION. 463 



approved practice of presidents of the British Association, to give an epitome of 

 some of the most remarkable recent additions to science : 



" To commence, then, with Astronomy : — The career of planetary discovery, 

 which began in the first years of the present century, and was resumed in 1845, has 

 since continued with unabated ardour. But since 1846 not a single year has 

 passed without some one or more additions to the number of the planetoids ; and 

 in one year alone (1852), no fewer than eight such bodies were discovered. The 

 last year has furnished its quota of five, and in the present three more have been 

 found, one by Mr. Pogson, of Oxford, and the other two by M. Goldschtnidt, of 

 Paris. The known number of these bodies is now forty-five. Their total mass, 

 bowever, is very small. The diameter of the largest is less than forty miles, while 

 that of the smallest (Atalanta) is little more than four. These discoveries have 

 been facilitated by star-maps and star-catalogues, the formation of which they have 

 on the other hand stimulated. Two veiy extensive works of this kind are now in 

 progress — the Star Catalogue of M. Chacornac, made at the Observatory of 

 Marseilles, in course of publication by the French Government ; and that of Mr. 

 Cooper, made at bis observatory at Markree, in Ireland, which is now being 

 published by the help of the Parliamentary Grant of the Royal Society. It is a 

 remarkable result of the latter labour, that no fewer than seventy-seven stars, 

 previously catalogued are now missing. This, no doubt, is to be ascribed in part 

 to the errors of former observations ; but it seems reasonable to suppose that, to 

 some extent at least, it is the result of changes actually in progress in the Sidereal 

 System. The sudden appearance of a new fixed star in the heavens, its subsequent 

 change of lustre, and its final disappearance, are phenomena which have at all 

 times attracted the attention of astronomers. About twenty such have been 

 observed. Arago has given the history of the most remarkable, and discussed 

 the various hypotheses which have been offered for their explanation. Of these, 

 the most plausible is that which attributes the phenomenon to unequal brightness 

 of the faces of the star which are presented successively to the earth by the star's 

 rotation round its axis. On this hypothesis the appearance should be periodic. 

 M. Goldschmidt has recently given support to this explanation, by rendering it 

 probable that the new star of 1609 is the same whose appearance was recorded in 

 the years 393, *798, and 1203. Its period, in such case, is 405-|- years. The 

 greater part of the celestial phenomena are comprised in the movements of the 

 heavenly bodies and the configurations dependiug on them ; and they are for the 

 most part reducible to the same law of gravity which governs the planetary 

 motions. 



" But there are appearances which indicate the operation of other forces, and 

 Tvhich, therefore, demand the attention of the physicist — although, from their 

 nature, they must probably long remain subjects of speculation. Of these, the 

 spiriform nebulee, discovered by Lord Rosse, have been already referred to from 

 this chair, as indicating changes in the more distant regions of the universe, to 

 which there is nothing entirely analogous in our own system. These appearances 

 are accounted for, by an able anonymous writer, by the action of gravitating forces 

 combined with the effects of a resisting medium — the resistance being supposed to 

 bear a sensible proportion to the gravitating action. 



" The constitution of the central body of our own system presents a nearer and 

 more interesting subject of speculation. Towards the close of the last century 

 many hypotheses were advanced regarding the nature and constitution of the sun, 



