t)() ON THE APPARENT FIGURE OF STARS. 



farther, its dimensions are changed, and the flame appears 

 broader, as at fig. 5. Lastly, on retiring still farther, it assumes 

 the figure of a lozenge, as at fig. Q j and at a greater distance it 

 begins to exhibit cross rays. 



The distance at which these cross rays begin to appear, is 

 different with different people', I have always observed them, 

 when I was twenty-five or thirty yards from a candle, and when 

 consequently its flame was seen under an angle of one or two 

 minutes. Some distinguish these rays at a shorter distance ;^ 

 others do not b?gin t(j perceive them till they are much farther 

 ofif*. 



The length of the rays issuing from the stars is so much the 



greater, in proportion to their brightness, and to the darkness 



of the night. The luminous rays of candles, torches, and 



bodies on fire, diminish in length in proportion to the intensity 



of their light j but we see those of the stars increase from the 



time of twilight, when they begin to be perceptible, to the 



time when the night is very dark. 



, . , If we look through a body of clear water, or any transparent 



Luminous ob- o j / r ^ 



jects seen substance, at a star or bright light, that would appear to give 



through a out long luminous rays to the naked eye: we shall perceive, 

 transparent , °, , . , . ,...,. . , 



substance. that the length oi tneir rays diminishes, in proportion as the 



thickness of the body of water, or transparent substance, 

 through which they are seen, is increased. 

 Star seen ^ ^^^^ ^^^" through a telescope, the object glass of which, 



through a te- being of large diameter, increases considerably the intensity of 

 escope. j^g jjgijj. g^ jjg focus, appears to be accompanied with four or 



more luminous rays. But if the intensity of the light be di- 

 minished, either by lessening the diameter of the object glass, 

 intercepting a part of its light, enlarging the surface of the 

 image, or any other roethod, we find the length of the rays 

 gradually diminish, till, the intensity of the light not being suf- 

 ficiently great, the rays cease to be perceptible • and then the 



* Is not this appearance of luminous objects seen at a distance, the 

 origin of the figure under which stars are generally represented, 

 though we have every reason to believe, that their form is spheroidal? 

 Is it not their different appearance to diflereat eyes, that has given rise 

 to their being represented with a difierent number of rays ? And is it 

 not because most people perceive five rays, that they ace usually deli- 

 neated with this number ? 



Star 



