616 Mr. William Euggins [May 13, 



stars, tlie creations of a day, or but the transient outbursts into 

 splendour of small stars usually invisible ; and, indeed, whether they 

 may be but extreme cases of the large class of variable stars v^hich 

 wax and wane in periods more or less regular. 



In the case of the more modern temporary stars the evidence 

 is forthcoming that they did exist before and do exist still. The 

 star of 1866 may be seen as one of about the ninth magnitude, with 

 nothing to distinguish it from its fellows. So the star of 1876 

 in Cygnus, which rose to the third magnitude, is still there as a star 

 of about the fourteenth magnitude. To these may be added, perhaps, 

 Tycho's star. 



The new star which makes the present year memorable is, 

 indeed, so far as our charts go, without descent. But there is no 

 improbability in assuming that in its usual low estate, to which it 

 has now returned, it is of smaller magnitude than would bring it 

 within our catalogues and charts. 



Of great value in similar cases, in the future, will be the plates of 

 the International Star Chart, which begins its existence this year. 

 Such a photographic record, like the partial ones already made at 

 the Cape Observatory and at the Harvard Observatory, will enable 

 us to put back at will the dial of time, and to re-observe the heavens 

 as they appeared when the plates were taken. 



The absence of any previous record of the new star of the present 

 year is not necessarily to be regarded as a proof that it did not 

 exist as a star emitting light. Visibility and invisibility in our 

 largest instruments are but expressions in terms of the power of the 

 eje. The photographic plate, untiring in its power of accumulation, 

 has brought to our knowledge multitudes of stars which shine, but 

 not for us. The energy of their radiation is too small to set up the 

 changes in the retina upon which vision depends. 



A striking illustration is presented by plates taken of tlie 

 neighbourhood of rj Argus by Mr. Kussel at Sydney, and later by Dr. 

 Gill at the Cape. In these photographs a crowd of stars reveal 

 themselves for the first time, which have hitherto shone in vain for 

 the dull eye of man. , 



It is not improbable that the new star in Auriga did exist as 

 a very faint star ; but what were the conditions under which it woke 

 up into sudden splendour ? Such information as is forthcoming has 

 been gained chiefly from that particular application of the spectro- 

 scope by which we can measure motion in the line of sight. It is 

 not too much to say that this method of observation has opened for 

 us in the heavens a door through which we can look upon the 

 internal motions of binary and multiple systems of stars, which 

 otherwise must have remained lor ever concealed from us. 



With every increase of telescopic aperture more stars are resolved 

 into double or multiple systems, but no conceivable progress in 

 instrument-making could have put it in our power, as the spectro- 

 scope does, to discover within the point-like image of a star, in many 



