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and the observer, obscuring its light. During twenty minutes that 

 Lord Darnley observed the phenomenon, it seemed to proceed through 

 its whole extent from north to south, its edges, which, when first ob- 

 served, extended equally on either side of Castor and Pollux, having 

 in that time entirely left the most northern of those stars. It had 

 wholly disappeared before ten o'clock. 



Lord Darnley did not see the beginning of the phenomenon ; but 

 was informed that it appeared at first like the moon rising, and gra- 

 dually extended from the eastern to the opposite horizon. The re- 

 flection thrown on the earth was faint : the degree and colour of the 

 light may be compared to that of a comet ; of greater brilliancy, how- 

 ever, than any that has appeared in this century. 



In a postscript, His Lordship states, that precisely the same ap- 

 pearance was observed at Castlereah, distant sixty miles ; and, ac- 

 cording to a Carlisle paper, somewhere in the North of England ; 

 the time of appearance in both cases corresponding very nearly with 

 that of his own observation. 



A paper was also read, entitled, " On the Magnetic Power of Soft 

 Iron." By Mr. Francis Watkins. Communicated bv Michael Fara- 

 day, Esq. D.C.L. F.R.S. 



When free magnetism is developed by induction, and is not re- 

 tained in that state by what has been termed the coercive force of 

 hard steel, it has generally been considered that all the phenomena 

 due to the existence of free magnetism cease on the removal of the 

 inducing cause. The object of the present communication is to show 

 that such is not the fact. From a variety of experiments described 

 by the author, it appears that soft iron continued to exhibit strongly 

 the attraction due to the developement of magnetism long after the 

 means by which the magnetism had been originally excited had ceased 

 to act. In these experiments, bars of soft iron, in the form of a horse- 

 shoe, had a single helix of copper wire wound round them, so that 

 on the ends of the wire being brought into contact with the poles of 

 a voltaic battery, the iron became an electro-magnet. With one of 

 these horse-shoes, while the connexion between the ends of the helix 

 and the poles of the battery existed, the soft iron, having a keeper 

 applied to its poles, supported 125 pounds ; it supported 56 pounds 

 after that connexion had been broken, and continued to retain the 

 power of supporting the same weight after an interval of several days, 

 care having been taken not to disturb, during the time, the contact 

 between the horse-shoe and its keeper. On this contact, however, 

 being broken, nearly the whole attractive power appeared to be im- 

 mediately lost. The author describes several instances of the same 

 kind, particularly one in which the contact between the ends of the 

 horse-shoe of soft iron and its keeper having been undisturbed during 

 fifteen weeks, the attractive power continued undiminished. Although 

 the interposition of a substance, such as mica or paper, between the 

 ends of the horse-shoe and its keeper necessarily diminished the force 

 of attraction, it did not appear to diminish the power of retaining that 

 force. In a case where the electro-magnet of soft iron and its keeper 

 were equal semi-circles, the author found, what may appear singular, 



