Page:Melbourne and Mars.djvu/58

56 moments we were in a small air boat going towards a mountain that on one side bounded our horizon. In an hour we landed on the top of it.

'What think you of the view?' asked Grayson.

'It is far the vastest I have seen, and with the ocean and sky on one hand, and the great plain all around, it can be called grand. But it is beautiful also, for I do not see a space of neglected or uncultivated ground.'

'Quite true. I brought you here to show you one of the greatest works ever attempted by man. For several thousands of years this was a desolate swamp; prior to that time it was a shallow sea, and earlier still a deep sea. To explain these changes I should have to go into the geological history of the planet, with which you are already conversant. For you have been taught that at one time we had more sea than land, and that water in actual quantity and in space occupied is gradually but surely diminishing.'

'Yes. Gaston, our teacher, told us that in one of his delightful talk; he also said that the human and other dwellers on our planet at that time had more water in their composition.'

'He was right: and what was true of our planet then is true of the earth at present. The body in which you spent half-an-hour the other day is four-fifths water, the one in which you dwell to-day has a higher temperature, is less dense, is lighter and more active, and is not quite half water. Possibly nature means something by making changes of structure come about gradually with changes of surroundings. But we are here to study a work of man as helping nature. All the land that we see from this mountain top, and thousands of miles that we cannot see, lay for thousands of years a pestivorous swamp. Here and there was a deep lagoon, and here and there a patch of tropical forest. Reptiles, wading birds, deadly snakes, were the principal inhabitants of this vast area. For hundreds of miles on all sides the land was rendered unhealthy by this dreadful space that seemed not to know whether to be water or land. The wind that passed over this region carried miasma and death with it upon all Bides. People had to live in this miasmatic area, for the soil was rich and bread was wanted. Thousands of deaths occurred every year from atmospheric poisoning and still the land was tilled, and in a while people were bred who seemed to thrive on poison.'

'That I should call a case of local adaptation. A moment ago you spoke of planetary adaptation of structure to surroundings.'

'Just so. It is a question of time and degree: in one a modification of heredity renders a few families incapable of suffering certain complaints; in the other whole species and races, of beings subdue themselves and their surroundings by adaptation of one to the other by gradual, and probably almost imperceptible changes.'

'And how was this great change finally brought about? How do we