president's address. 29 



Some recent photographs that I have seen exhibit the peculiar 

 spots and other features of this planet with a remarkable 

 clearness of definition. 



But perhaps one of the most interesting of aU the recent 

 discoveries, relating to the solar system, is that of the minor 

 planets, of which up to the present time 309 have been detected. 

 These minute bodies, supposed to vary in their diameter from 

 about twenty to two hundred miles, are all included between the 

 orbits of Mars and Jupiter. The first four of the minor planets 

 were discovered near the beginning of the present century, and 

 for sometime were considered to be fragments of a large planet 

 shattered to pieces by some internal convulsion ; but owing to 

 the great diversity in the observed inclinations and other 

 elements of their orbits, this hypothesis is hardly tenable. I 

 remember very distinctly the enthusiasm with which the discovery 

 of a fifth member of the group in 1845 was received, the first 

 of the yearly discoveries that have been made to the present 

 time. While watching one of these minute objects in the 

 transit-circle at Grreenwich, it has always appeared to me that 

 the general truth of the fundamental laws of astronomy is 

 made apparent, when the faint point of light representing a 

 minor planet faithfully enters the field of view at the exact 

 moment, and in the exact position in the heavens to which the 

 telescope is directed, as predicted by the computer, with the 

 same accuracy as the large planets. The elements of the orbits 

 of all these 309 minor planets have been calculated, some of 

 them with great precision. 



Minor planets, however, are not the only minute bodies 

 circulating in orbits around the sun, for within the confines of 

 our solar system, swarms of meteors are now known to move in 

 periodic orbits, accompanied by comets travelling in the midst 

 of the swarm. Comets and meteors are therefore supposed to 

 be physically connected. Indeed, the elements of the orbits of 

 several comets are found to be almost identical with those of 

 corresponding streams of meteors, and spectrum analysis has 

 proved that their elementary composition has much in common. 

 Prof. Lockyer, however, has expresssed an opinion that all self- 

 luminous bodies in the celestial vault may probably be composed 

 of meteorites or masses of meteoritic vapour, produced by heat 



