162 Star anfr Meatber Gossip 



applause that shook the great theatre when he finished 

 reciting Bichter's Dream of the overpowering effect 

 of the universe upon the human mind. 



TELESCOPES AND TEMPERATURE 



The silvered-glass speculum is known to be incon- 

 veniently subject to changes of temperature. Special 

 study has been given to the matter by the Rev. 

 W. F. A. Ellison, of Fethard-on-Sea, Waterford, who 

 holds that a change of two degrees Fahrenheit has a 

 very visible effect, whilst one of ten degrees will 

 render the best figured mirror ever made temporarily 

 useless. The physical properties of glass account for 

 this. The astronomer working with a clear night -sky 

 does so under conditions which usually mean a falling 

 temperature, and a falling temperature affects his 

 mirror. On some clear nights, Mr. Ellison submits, a 

 large telescope is almost useless. The " seeing is bad," 

 and the general cause of it is the mingling of air 

 currents of varying temperatures and densities. 

 " Sometimes the drifting of an air current of a different 

 density from the rest of the atmosphere across celestial 

 objects can be clearly seen through a telescope." 



In writing to me on the subject, Mr. Ellison said 

 (December 9th, 1914): "Any person who possesses 

 a reflector can, if he chooses to watch for them, and 

 is able to recognise the symptoms, observe for him- 

 self the fluctuations of figure due to changes of air 

 temperature, and draw the inevitable inference that 

 a star test may pronounce one and the same mirror 

 over-corrected at one time and under-corrected at 

 another, and that as a direct consequence the only 



