The Romance of the Heavens 29 



space on the opposite side. We are not sure. The surface of 

 Venus is so bright the light of the sun is reflected to us by such 

 dense masses of cloud and dust that it is difficult to trace any 

 permanent markings on it, and thus ascertain how long it takes 

 to rotate on its axis. Many astronomers believe that they have 

 succeeded, and that the planet always turns the same face to the 

 sun. If it does, we can hardly conceive of life on its surface, in 

 spite of the cloud-screen. 



We turn to Mars ; and we must first make it clear why there 

 is so much speculation about life on Mars, and why it is supposed 

 that, if there is life on Mars, it must be more advanced than life 

 on the earth. 



Is there Life on Mars? 



The basis of this belief is that if, as we saw, all the globes in 

 our solar system are masses of metal that are cooling down, the 

 smaller will have cooled down before the larger, and will be 

 further ahead in their development. Now Mars is very much 

 smaller than the earth, and must have cooled at its surface millions 

 of years before the earth did. Hence, if a story of life began on 

 Mars at all, it began long before the story of life on the earth. 

 We cannot guess what sort of life-forms would be evolved in a 

 different world, but we can confidently say that they would tend 

 toward increasing intelligence; and thus we are disposed to look 

 for highly intelligent beings on Mars. 



But this argument supposes that the conditions of life, 

 namely air and water, are found on Mars, and it is disputed 

 whether they are found there in sufficient quantity. The late 

 Professor Percival Lowell, who made a lifelong study of Mars, 

 maintained that there are hundreds of straight lines drawn across 

 the surface of the planet, and he claimed that they are beds of 

 vegetation marking the sites of great channels or pipes by means 

 of which the "Martians" draw water from their polar ocean. Pro- 



