THE MOON LANDSCAPE 15 



terial, and we may conceive that a cracking and crttmbling of the 

 more brittle constituents would ensue, together with a grating of 

 contiguous but disconnected masses, and an occasional dislocation 

 of them. We refer again to these phenomena to remark that if an 

 atmospheric mediimi existed they would be attended with noisy 

 manifestations. There are abundant causes for grating and 

 crackling sounds, and such are the only sources of noise upon the 

 moon where there is no life to raise a hum, no wind to murmur, 

 no ocean to boom and foam, and no brook to plash. Yet, even 

 these crust-crackling commotions, though they might be felt by 

 the vibrations of the ground, would not manifest themselves 

 audibly, for without air there can be no communication between 

 the grating or cracking body and the nerves of hearing. Dead 

 silence reigns on the moon; a thousand cannons might be fired 

 and a thousand drums beaten upon that airless world, but no sound 

 could come from them: lips might quiver and tongues essa}^ to 

 speak, but no action of theirs could break the utter silence of the 

 lunar scene. 



At a rate 28 times slower than upon earth, the shadows shorten 

 till the sun attains his meridian height, and then, from the tropical 

 region upon which we have in imagination stood, nothing is to be 

 seen on any side, save towards the black sky, but dazzling light. 

 The relief of afternoon shadow comes but tardily, and the darkness 

 drags its slow length along the valleys and creeps sluggishly up 

 the mountain sides till, in a hundred hours or more, the time of 

 sunset approaches. This phenomenon is but daybreak reversed, 

 and is unaccompanied by any of the gorgeous sky tints that make 

 the kindred event so enrapturing on earth. The sun declines 

 towards the dark horizon without losing one jot of its brilliancy, 

 and darts the full intensity of its heat upon all it shines on to the 

 last. Its disc touches the horizon, and in half an hour dips half- 

 way beneath it, its intrinsic brightness and color remaining un- 

 changed. The brief interval of twilight occurs, as in the morning, 

 when only a small chord of the disc is visible, and the long shadows 

 now sharpen as the area of light that casts them decreases. For a 

 while the zodiacal light vies with the earth-moon high in the 

 heavens in illuminating the scene, but in a few hours this solar 

 appendage passes out of view, and our world becomes the queen 

 of the lunar nij/ht. 



