426 VARIABLE STARS IN SOUTHERN HEMISPHERE, 



two necessarily imaginary positions. But it is clearly evident 

 from this paper that such is not the case ; and that his symbo- 

 lical analysis labours under the defect of grasping some extra- 

 neous kindred problem. However, Sir William's method led 

 him to discover theorem 27 as respects the particular state of 

 the data considered : but he does not seem to have observed 

 that the closing chords are all in plane with the line of contact 

 of the surfaces. 



The solutions which I give to the general problem are ex- 

 tremely simple ; and the numerous new and beautiful theorems 

 unfolded bear testimony to the power of the system of " Geome- 

 tric Superieure " of the modern French School. 



On the desirability of a systematic search for, and observation 

 of variable stars in the Southern Hemisphere, by ME. 

 JOHN TEBBUTT, JUNR. 



[Read August 13th. 1862.] 



THE department of Astronomy relating to variable stars was 

 very little followed up before the middle of the present century. 

 The most complete catalogue that I have yet seen of such objects 

 is that contained in Mr. George F. Chambers' admirable hand- 

 book of Astronomy, published at the close of last year. It 

 comprises 99 stars. Of 22 the dates of discovery are not given, 

 18 were discovered previous to 1800, and the remaining 59 were 

 discovered during the present century. If we divide the elapsed 

 portion of the present century into periods of ten years, we shall 



