478 THE POPULAR SCIENCE MONTHLY. 



ASTRONOMY WITH AN OPERA-GLASS. 



THE MOON AND THE SUN. 



By GAEKETT P. SEKVISS. 



4 i -r-'p j s a mos t beautiful and delightful sight," exclaims Galileo, in 

 -L describing the discoveries he had made with his telescope, " to 

 behold the body of the moon, which is distant from us nearly sixty 

 semi-diameters of the earth, as near as if it was at a distance of only 

 two of the same measures. . . . And, consequently, any one may know 

 with the certainty that is due to the use of our senses that the moon 

 assuredly does not possess a smooth and polished surface, but one 

 rough and uneven, and, just like the face of the earth itself, is every- 

 where full of vast protuberances, deep chasms, and sinuosities." 



There was, perhaps, nothing in the long series of discoveries with 

 which Galileo astonished the world after he had constructed his tele- 

 scope, which, as he expresses it, " was devised by me through God's 

 grace first enlightening my mind," that had a greater charm for him 

 than his lunar observations. Certainly there was nothing which he 

 has described with greater enthusiasm and eloquence. And this could 

 hardly have been otherwise, for the moon was the first celestial object 

 to which Galileo turned his telescope, and then for the first time 

 human eyes may be said to have actually looked into another world 

 than the earth, though his discoveries and those of his successors have 

 not realized all the poetic fancies about the moon contained in the 

 verses that are ascribed to Orpheus : 



" And he another wandering world has made 

 Which gods Selene name, and men the moon. 

 It mountains, cities has, and temples grand." 



Yet Galileo's observations at once upset the theory, for which Apollo- 

 nius was responsible, and which seems to have been widely prevalent 

 up to his time, that the moon was a smooth body, polished like a 

 mirror, and presenting in its light and dark spots reflections of the 

 continents and oceans of the earth. lie also demonstrated that its sur- 

 face was covered with plains and mountains, but the " cities and 

 temples " of the moon have remained to our time only within the ken 

 of romance. 



Galileo's telescope, as I have before remarked, was, in the principle 

 of its construction, simply an opera-glass of one tube. He succeeded 

 in making a glass of this kind that magnified thirty diameters, a very 

 much higher power than is given to the opera- and field-glasses of to- 

 day. Yet he had to contend with the disadvantages of single lenses, 

 achromatic combinations of glass for optical purposes not being con- 



