378 FROM NEBULA TO NEBULA 



by a diminution of the general brilliancy of the whole area. We 

 might naturally expect therefore that some snowy areas would 

 appear to be brighter than others. * * * 



A very casual examination of the Moon will show that un- 

 der high illumination nearly half of the craters exhibit white 

 patches on portions of their interior slopes. Very little attention 

 has ever been paid to them by selenographers. They are some- 

 times visible as soon as the Sun rises upon them, but more often 

 they gradually develop under the action of the solar rays. They 

 lie on the slopes most directly exposed to the Sun, and as the 

 Sun moves across the lunar sky, they shift from the eastern to 

 the western side of the craters. In the southern hemisphere 

 they circle round the crater by way of the south, and in the 

 northern by way of the north. Even quite near the equator the 

 circling occurs to a certain extent. The whiteness is frequently 

 due to small irregularly shaped bright areas, which are some- 

 times related to small craters, but more often they lie on some 

 steeply inclined interior slope. They rarely occur on the outer 

 slopes of the craters. 



Let one more quotation suffice, this time from the 

 article of Professor Eussell W. Porter, entitled Moon- 

 scapes (Pop. Astr. t No. 238), which is embellished with 

 three instructive ideal views of the moon that cannot be 

 distinguished from Arctic landscapes, or rather snow- 

 scapes. He says: 



Our nearest neighbor, the moon, is a case in point. The 

 writer, in viewing her surface through his sixteen inch reflector 

 in the comfort of a closed observing room, has frequently caught 

 himself transported to that body, and, in imagination, viewing 

 her scenery from some crater lip or the vast expanse of one of 

 her sea floors. Having himself spent many years above the Arctic 

 Circle, he was struck by a strange likeness of the moon's general 

 aspect to our own polar regions. The long reaches of the frozen 

 polar ocean, traversed by immense pressure ridges and tidal 

 cracks, the dazzling whiteness and clear cut shadows, the desola- 

 tion and loneliness all seemed to find a counterpart in the lunar 

 appearance. The accompanying moonscapes were the natural out- 

 come. 



CURRENT THEORIES BEGARDING THE LUNAR SURFACE 



THE PLUTONIC OR VOLCANIC THEORY. Since, in our 

 superlatively practical age, we find astronomers, even 

 those of an agnostic turn, ready to subscribe to such 



