CHAPTER I. THE EVE OF THE WAR No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own. That as men busied themselves about their various concerns, they were scrutinized and studied perhaps almost as narrowly as a man with a microscope might scrutinize the transient creatures that swarm and multiply in a drop of water. With infinite complacency men went to and fro over this globe with their little affairs, serene in their assurance of their empire over matter. It is possible that the emphusoria under the microscope do the same. No one gave a thought to the older worlds of space as sources of human danger, or thought the idea of life upon them as impossible or improbable. It is curious to recall some of the mental habits of those departed days. At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise. Yet, across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic regarded this earth with envious eyes and slowly and surely drew their plans against us. And early in the 20th century came the great disillusionment. The planet Mars, I scarcely need to remind the reader, revolves about the sun at a mean distance of 140 million miles, and the light and heat it receives from the sun is barely half of that received by this world. It must be if the nebular hypothesis has any truth, older than our world, and long before this earth ceased to be molten, life upon its surface must have begun its course. The fact that it is scarcely one seventh of the volume of the earth must have accelerated its cooling to the temperature at which life could begin. Yet so vain is man, and so blinded by his vanity, that no writer, up to the very end of the 19th century, expressed any idea that intelligent life might have developed there, far or indeed at all, beyond its earthly level. Nor was it generally understood that since Mars is older than our earth, with scarcely a quarter of the superficial area and a quarter of the vastness of the earth, it is not possible that, in the same area, and remoter from the sun, it necessarily follows that it is not only more distant from time's beginning, but nearer its end. The secular cooling that must someday overtake our planet has already gone far indeed with our neighbour. Its physical condition is still largely a mystery, but we know now that even in its equatorial region, the midday temperature barely approaches that of our coldest winter. The temperature has become much more attenuated than ours. Its oceans have shrunk until they cover but a third