338 



POPULAR SCIENCE MONTHLY. 



lunar globe. Nobody who has not seen the moon with a telescope 

 — it need not be a large one — can form a correct and definite idea 

 of what the moon is like. 



The satisfaction of viewing with one's own eyes some of the 

 things the astronomers write and talk about is very great, and the 

 illumination that comes from such viewing is equally great. Just 

 as in foreign travel the actual seeing of a famous city, a great gal- 

 lery filled with masterpieces, or a battlefield where decisive issues 

 have been fought out illuminates, for the traveler's mind, the 

 events of history, the criticisms of artists, and the occurrences of 

 contemporary life in foreign lands, so an acquaintance with the 



sights of the heavens gives a 

 grasp on astronomical prob- 

 lems that can not be ac- 

 ([uired in any other way. 

 The person who has been in 

 Rome, though he may be no 

 archseologist, gets a far more 

 xivid conception of a new 

 iliscovery in the Forum than 

 does the reader who has 

 never seen the city of the 

 Seven Hills; and the ama- 

 teur who has looked at Jupi-" 

 ter with a telescope, though 

 he may be no astronomer, 

 finds that the announcement 

 of some change among the 

 wonderful belts of that cloudy planet has for him a meaning and 

 an interest in which the ordinary reader can not share. 



Jupiter is perhaps the easiest of all the planets for the amateur 

 observer. A three-inch telescope gives beautiful views of the 

 great planet, although a four-inch or a five-inch is of course better. 

 But there is no necessity for going beyond six inches' aperture in 

 any case. For myself, I think I should care for nothing better 

 than my five-inch of fifty-two inches' focal distance. "With such 

 a glass more details are visible in the dark belts and along the 

 bright equatorial girdle than can be correctly represented in a 

 sketch before the rotation of the planet has altered their aspect, 

 while the shadows of the satellites thrown upon the broad disk, 

 and the satellites themselves when in transit, can be seen some- 

 times with exquisite clearness. The contrasting colors of various 

 parts of the disk are also easily studied with a glass of four or fivc^ 

 inches' aperture. 



Jupiter seen with a Five-Inch Telescope. 

 Shadow ot a satellite visible. 



