124 THE PLANET MAES: IS IT INHABITED? 



Three great dark rifts were also seen during the last opposition of 

 Mars, one increasing in nine days from one hundred miles to 

 three hundred and fifty miles. This again points to the existence 

 of hilly portions near the South Pole, the dark rifts doubtless 

 showing where the ground was low, and from which consequently 

 the snow had disappeared most quickly. 



During the opposition named, 1894-5, it was remarked that the 

 South Polar Cap did not extend symmetrically round the pole. In 

 long. 206, the snow extended only to lat. 71, or 19 degrees (six hun- 

 dred and ninety-eight miles) from the Pole, answering to our North 

 Cape ; whereas in longitude 26 it extended to 54^, or 35^ degrees 

 (one thousand three hundred and four miles) from the Pole, answer- 

 ing to our British Columbia. Comparing these with our terrestrial 

 snows, we note that here in Yorkshire, 36 degrees (two thousand 

 five hundred miles) from North Pole, we have frequently rigorous 

 winters of snow and ice; and even in New York, 50 degrees 

 (three thousand four hundred and seventy-five miles) from the Pole, 

 the snowstorms are now and then appalling in their severity. It 

 should be remembered that a degree on Mars measures thirty-six 

 and three-quarter miles, against sixty-nine and a-half miles upon 

 Earth. Why the Martian snow-caps should thus extensively 

 diminish in area during summer (actually disappearing in 1894, 

 for the first time known to astronomers), as proportionately con- 

 trasted with the perennial ice-caps of Earth, has not yet been 

 satisfactorily explained. According to accepted theory, the cold at 

 the Martian poles, owing to much greater distance from the Sun 

 than Earth, also to the thinness of its atmosphere, should be con- 

 tinuously much more severe — that is, far below freezing point. A 

 partial explanation has been found in the thinness of the ice-coat- 

 ing, due to the limited quantity of water-vapour which its atmo- 

 sphere can carry and deposit as snow ; also, in the absence of a 

 deep Arctic ocean, in which more ice would, almost certainly, be 

 formed in winter than could be melted during each succeeding 

 summer. 



Some years ago, as many of our readers will remember, there 

 was much talk amongst a section of the public about signalling to 

 Mars, by arranging upon some vast plain certain geometrical 

 figures, which, when seen by Martians, would testify to the exist- 



