THE IMPENETRABLE SEA 



Nearest to the sun, yet actually revolving 36 million 

 miles from it, we see Mercury, with a diameter of 

 3,100 miles: a planet not much larger than our moon. 

 Keeping one hemisphere forever turned towards the sun. 

 Mercury has no day or night, and one side is therefore 

 fiercely scorched, blazing with intense light and heat, 

 while the other is forever shrouded in darkness. Although 

 Schiaparelli and Antoniada imagined they saw clouds 

 on Mercury's darker side, Dolfus, in 1953, dismissed the 

 idea. It is now certain that water-droplets on Mercury 

 would be as short-lived as snowflakes in a blast-furnace. 



Moving away from the sun we come to Venus, with a 

 diameter (7,575.4 miles) only slightly less than that of 

 our own world. It is 67 million miles from the sun, and 

 sometimes approaches to within 25 million miles of our 

 earth. Astronomers have thought that the clouds which 

 continually obscure its shining face might be composed 

 of water- vapour and that parts of its surface might even 

 be covered with water. But such probabilities have been 

 shown in quite recent years to be very remote. Exhaustive 

 investigation of the planet's atmosphere by means of the 

 spectograph has shown neither water-vapour nor oxygen 

 in detectable amounts. In fact recent researches have 

 detected the presence of several hundred times as much 

 carbon dioxide in its atmosphere as the amount present 

 in our own. 



That the surface of Venus is desert-like, and that high 

 winds may easily account for clouds (which are not of 

 water-vapour but of dust) seems as good a guess as any. 

 Certainly there is no evidence whatever, as the result of 

 investigations to date, of the existence of lakes on its 

 surface, much less oceans. 



Mars, on the other side of our world, outward from 

 the sun and 142 million miles from it, is 35 million miles 

 from our earth at its nearest. It certainly has water, but 

 it seems certain that it has no oceans and that any water 

 it possesses can only be present in limited quantities — in 



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