ADDRESS. lxiii 



ficicntly powerful to penetrate these depths of space. Those four indivi- 

 duals are the Herschefs, father and son, Lord Rosse, and Mr. Wm. Lassell. 

 That praiseworthy nobleman, Lord Rosse, began his meritorious career by 

 obtaining a First Class at this University, and has, as you know, spent large 

 sums of money and displayed considerable mechanical genius in erecting, 

 near his own Castle in Ireland, an instrument of far greater power than any 

 other in the world ; and with it he has observed these nebulae, and employed 

 skilful artists to delineate their forms : and he has moreover made the very 

 curious discovery, that some of them are arranged in a spiral form, a fact 

 which gives rise to much interesting speculation on the kind of forces by 

 which their parts are held together. It were much to be wished that obser- 

 vations similar to these, and with instruments of nearly the same power, 

 should be made of the Southern nebulas also; that this generation might 

 be able to leave to posterity a record of their present configurations. The 

 distinguished Astronomer, Mr. Wm. Lassell, the discoverer of Neptune's 

 satellite, has just finished at his own cost an instrument equal to the task, 

 mounted equatorially ; and I am not without hope that it may, at perhaps 

 no very distant period, be devoted to its accomplishment. A recent com- 

 munication from him to the Astronomical Society expresses satisfaction with 

 the mounting of his instrument, and after many trials its great speculum has 

 at last come forth nearly perfect from his laboratory. 



I am, however, warned by the lapse of time, that it will not be possible for 

 me to exhaust the whole field, the limits of which I have sketched, in which 

 private enterprise has been assiduously at work to enlarge the bounds of 

 astronomical knowledge. I will therefore pass at once to the two most in- 

 teresting subjects which remain, the observations of Comets, and of peculiar 

 appearances on the Sun's disc. 



Of all the phenomena of the heavens, there are none which excite more 

 general interest than comets, those vagrant strangers, the gipsies as they 

 have been termed of our solar system, which often come we know not whence, 

 and at periods when we least expect them : and such is the effect produced 

 by the strangeness and suddenness of their appearance, and the mysterious 

 nature of some of the facts connected with them, that while in ignorant times 

 they excited alarm, they now sometimes seduce men to leave other employ- 

 ments and become Astronomers. Now, though the larger and brighter 

 comets naturally excite most general public interest, and are really valuable 

 to astronomers, as exhibiting appearances which tend to throw light on the 

 internal structure of these bodies, and the nature of the forces which must 

 be in operation to produce the extraordinary phenomena observed, yet some 

 of the smaller telescopic comets are, perhaps, more interesting in a physical 

 point of view. Thus the six periodical comets, the orbits of which have been 

 determined with tolerable accuracy, and which return at stated intervals, are 

 extremely useful as being likely to disclose facts, of which but for them we 

 should possibly have ever remained ignorant. Thus, for example, when the 



