BY JOHN TEBBUTT, JTJX. 135 



perceived with difficulty by the naked eye ; the difference 

 between any two consecutive magnitudes should be so small as 

 not to admit with accuracy of any intermediate order of magni- 

 tude. All the other stars should then be arranged under the 

 standard stars to which they are respectively considered to be 

 equal. A mere isolated comparison of two stars, without refer- 

 ence to other stars of the. same class, and to the higher and 

 lower orders of magnitude, would hereafter leave the observer in 

 doubt as to which of the two stars was the variable one, and as 

 to their limits of magnitude. In making a series of comparisons 

 recourse might be had to the very simple and inexpensive 

 astrometer devised and employed by Sir John Herschell at the 

 Cape of Good Hope. A description of this instrument may be 

 found in his " Outlines of Astronomy," or in his " Results of 

 Observations made at the Cape of Good Hope," &c. To those 

 amateurs who would undertake a comparison of the stars in the 

 Southern Hemisphere, a study of Sir John Herschell's " Method 

 of Sequences " will be profitable, and the results of the labours of 

 that great authority valuable for reference. 



A new and interesting feature iii the department of stellar 

 astronomy has, I believe, been brought to light by the observations 

 of Mr. Abbott, of Tasmania, as the following extract from the 

 Herald, of June 23rd last will show : 



" At a meeting of the Royal Society of Tasmania, on the 3rd 

 instant, Mr. Abbott read some notes on a drawing of the ' cluster 

 of coloured stars surrounding Kappa (/c) Crucis,' the object being 

 to show that considerable alteration had taken place both in the 

 position and colouring of its component stars since it was observed 

 by Sir John Herschell at the Cape of Good Hope." 



If the component stars of the cluster Kappa (/e) Crucis have 

 really undergone changes in their position and colouring, surely it 

 is a discovery of the highest interest in stellar astronomy. May 

 we regard the cluster in question as a system of coloured suns, 

 revolving round their common centre of gravity, thus adding one 

 more example to the known variety and beauty of the Great 

 Creator's works ? 



It would be foreign to the object of this paper for me to enter 

 into any speculations regarding the causes of the phenomena of 



