THE POWERS OF TELESCOPES. 1 99 



examples of the greatest telescopes, in astronomical 

 observations, can hold a star within view 1000 times 

 as far off as it would be visible with the unaided eye. 

 While as regards the power of sea or field glasses: 

 the low-power binocular glass used now by mariners 

 has the seeming effect of reducing distance to about 

 one-third (that is to say, an object three miles off is 

 seen as if it were but one mile distant), and a good 

 hand-telescope of considerable magnifying power to 

 about one-tenth (i.e., an object ten miles off to apparently 

 one mile). * 



It will thus be seen that the power of a good hand 

 telescope is very great; and if the state of the atmo- 

 sphere is favourable there can be no question as to 

 its absolute superiority over the binocular field glass. 

 A stag for instance can be made out, lying upon a 

 mountain side, by the aid of the former, which would 

 probably escape detection with the latter. Indeed Mr. 

 Grimble, who is an authority on Scotch Highland 

 deerstalking, goes so far as to assert that, " Binoculars 

 of any sort are not of much use (on bare hillsides) as 

 they cannot be made powerful enough to distinguish 

 stags, etc., at any great distance." f 



We must however be permitted to point out that 

 this dictum (which we do not for one moment question 

 the correctness of) must be accepted by the hunter 

 with many reservations. If for instance it is foggy, 

 or the atmosphere upon a mountain is decidedly misty 

 in the distance, or if there happens to be any mirage 

 present on tropical plains: then a glass of this kind, 



* Extracts from Report on a Lecture on Astronomy and Telescopes, 

 by Sir Robert Ball, Astronomer Royal, in the Dublin Daily Express. 

 of November 9, 1889. 



\ Deer- Stalking, by Augustus Grimble, 1 886, p. 17. 



