DISTRIBUTION OF THE STARS. 



bright and large, and we call them stars of the first magnitude.. 

 Those which lie in the circuit beyond, and occupy a wider range, 

 are more numerous and less bright ; and we call them stars of the 

 second magnitude. And there is thus a progression increasing ia 

 number and distance and diminishing in brightness, until we 

 attain a distance so great that the stars are barely visible to the 

 naked eye. This is the limit of vision. It is the limit of the 

 range of the eye in its natural condition ; but an eye has been 

 given us more potent still, and of infinitely wider range, the eye- 

 of the mind. The telescope, a creature of the understanding, has 

 conferred upon the bodily eye an infinitely augmented range, 

 and, as we shall presently see, has enabled us to penetrate into 

 realms of the universe, which, without its aid, would never have 

 been known to us. But let us, however, pause for the present, 

 and dwell for a moment upon that range of space which comes 

 within the scope of natural vision. 



27. A planet, to the naked eye, with one or two exceptions,, 

 appears like a common star. The telescope, however, immediately 

 presents it to us with a distinct circular disc, similar to that 

 which the moon offers to the naked eye ; and in the case of some 

 of the planets, a powerful telescope will render them apparently 

 even larger than the moon. But the effect is very different 

 indeed when the same instrument is directed even to the brightest 

 star. We find that instead of magnifying, it actually diminishes. 

 There is an optical illusion produced when we behold a star, 

 which makes it appear to us to be surrounded with a radiation 

 which causes it to be represented, when drawn on paper, by a dot 

 with rays diverging on every side from it. The effect of the 

 telescope is to cut off this radiation, and present to us the star as 

 a mere lucid point, having no sensible magnitude ; nor can any 

 augmented telescopic power which has yet been resorted to, 

 produce any other effect. Telescopic powers, amounting to 6000, 

 were occasionally used by Sir William Herschel, and he stated 

 that with these the apparent magnitude of the stars seemed less, 

 if possible, than with lower powers. 



28. We have other proofs of the fact, that the stars have no- 

 sensible discs, among which may be mentioned the remarkable 

 effect called the oceultatibn of a star by the dark edge of the moon. 

 When the moon is a crescent, or in the quarters, as it moves over 

 the firmament, its dark edge successively approaches to, or 

 recedes from, the stars. And from time to time it happens that 

 it passes between the stars and the eye. If a star had a sensible 

 disc in this case, the edge of the moon would gradually cover it, 

 and the star, instead of being instantaneously extinguished, 

 would gradually disappear. This is found not to be the case; 



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