ASTRONOMY WITH AN OPERA-GLASS. 479 



trived until nearly a hundred years after his death, and so his tele- 

 scope did not possess quite as decided a superiority over a modern 

 field-glass as the difference in magnifying power would imply. In 

 fact, if the reader will view the moon with a first-rate field-glass, he 

 will perceive that the true nature of the surface of the lunar globe can 

 be readily discerned with such an instrument. Even a small opera- 

 glass will reveal much to the attentive observer of the moon ; but for 

 these observations the reader should, if possible, make use of a field- 

 glass, and the higher its power the better. The illustrations accom- 

 panying this article were made by the author with the aid of a glass 

 magnifying six diameters. 



Of course, the first thing the observer will wish to see will be the 

 mountains of the moon, for everybody has heard of them, and the 

 most sluggish imagination is stirred by the thought that one can look 

 off into the sky and behold " the eternal hills " of another planet as 

 solid and substantial as our own. But the chances are that, if left to 

 their own guidance, ninety-nine persons out of a hundred would choose 

 exactly the wrong time to see these mountains. At any rate, that is 

 my experience with people who have come to look at the moon through 

 my telescope. Unless warned beforehand, they invariably wait until 

 full moon, when the flood of sunshine poured perpendicularly upon the 

 face of our satellite conceals its rugged features as effectually as if a 

 veil had been drawn over them. Begin your observations with the 

 appearance of the narrowest crescent of the new moon, and follow it 

 as it gradually fills, and then you will see how beautifully the advanc- 

 ing line of lunar sunrise reveals the mountains, over whose slopes and 

 peaks it is climbing, by its ragged and sinuous outline. The observer 

 must keep in mind the fact that he is looking straight down upon the 

 tops of the lunar mountains. It is like a view from a balloon, only' at 

 a vastly greater height than any balloon has ever attained. Even with 

 a powerful telescope the observer sees the moon at an apparent dis- 

 tance of several hundred miles, while with a field-glass, magnifying six 

 diameters, the moon appears as if forty thousand miles off. The ap- 

 parent distance with Galileo's telescope was eight thousand miles. 

 Recollect how when seen from a great height the rugosities of the 

 earth's surface flatten out and disappear, and then try to imagine how 

 the highest mountains on the earth would look if you were suspended 

 forty thousand miles above them, and you will, perhaps, rather wonder 

 at the fact that the moon's mountains can be seen at all. 



It is the contrast of lights and shadows that not only reveals them 

 to us, but enables us to measure their height. On the moon shadows 

 are very much darker than upon the earth, because of the extreme 

 rarity of the moon's atmosphere, if indeed it has any atmosphere at 

 all. By stepping around the corner of a rock there, one might pass 

 abruptly from dazzling noonday into the blackness of midnight. The 

 surface of the moon is extraordinarily rough and uneven. It possesses 



