36 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



6. There is some probability that the electric currents 

 which give rise to auroras are propagated in a medium which 

 pervades all space, and that the spectrum of the aurora is in 

 reality the spectrum of that medium. 



7. It is not improbable that the tails of all large comets 

 will be found to give spectra similar to that of the aurora, 

 although additional lines may be present. 



SMALL PLANETS DISCOVERED IN 1872. 



During the year 1872 eleven additions were made to the 

 number of small planets known to revolve between Mars and 

 Jupiter, making the entire number now known 128. Their 

 numbers, discoverers, and dates of discovery are as follows : 



(118), JPeitho, by Luther, at Bilk, March 15. 



(119), by Watson, at Ann Arbor, April 3. 



(120), Lachesis, by Borelli, at Marseilles, April 10. 



(121), by Watson, at Ann Arbor, May 12. 



(122), Gerda, by Peters, at Clinton, July 31. 



(123), JBrurthilda, by Peters, at Clinton, July 31. 



(124), Alceste, by Peters, at Clinton, August 23. 



(125), by Prosper-Henry, at Paris, Sept. 11. 



(126), by Paul-Henry, at Paris, Nov. 5. 



(127), by Prosper-Henry, at Paris, Nov. 5. 



(128), by Watson, at Ann Arbor, Nov. 28. 



The numbers 126 and 127 are remarkable as being found 

 on the same evening so near together that they were in the 

 same field of view of the telescope. 



CABLE ANNOUNCEMENTS OP ASTRONOMICAL DISCOVERIES. 



Astronomers have been for some time interested in devis- 

 ing some method by which the discoveries of new planets or 

 comets in one hemisphere could be reported to the other with 

 the least possible delay, communication by mail being so 

 slow, comparatively, that the object materially changes its 

 place before the fellow-workers on the opposite side of the 

 Atlantic Ocean can direct their attention to it. The difficul- 

 ty is still greater when the bodies in question are faint, since 

 they are necessarily discovered in nights free from the light 

 of the moon; but before the news can be transmitted across 

 the water (requiring an interval of about two weeks) the 

 moon will so illuminate the sky as to prevent observers from 



