And then there is sound common sense which reasons so justly on account of the excellence of its education. “We are,” it says, “without doubt the most intelligent beings of creation. Why should other planets have the honour of being enriched by intellectual excellence such as ours? Can we even admit the existence of beings similar to ourselves?” No doubt one could perhaps remark that the most gifted nations of the Earth do not know how to conduct themselves, that their intelligence is chiefly exercised in devouring each other and in ruining themselves, that they mortgage the future like blind fools, that thieves are not uncommon, nor even murderers. But apart from that we are obviously very superior beings, and it is hardly likely that on any of the myriads of worlds which gravitate in the immensity of space nature should have given birth to intelligences of our calibre. Why therefore should we attempt an optical correspondence with the planet Mars? If it is inhabited, the inhabitants have not our powers, and our trouble would be thrown away. Even should they see our signals, they would never think that they were meant for them. Also, we shall never attempt it. * * * * * But is it possible that the inhabitants of Mars have already commenced and that it is we who do not understand? According to geological computations, the minimum age of the Earth as a habitable sphere since the formation of the first dry land is 20 million years: 10 million 700 thousand for the primordial age, 2 million 300 thousand years for the secondary age, 460 thousand years for the tertiary age, and 100 thousand for the quaternary age. Man has existed on Earth since the end of the tertiary age, that is over 100 thousand years. Astronomical instruments were only invented in 1609, and Mars was not observed nor recognised in its principal geographical details until 1858. Complete observations of Martian geography only date back to 1862. The first detailed triangulation of the planet, the first map comprising the smallest objects visible in the telescope and measured by micrometer was only commenced in 1877, continued in 1879, and completed in 1882. It is therefore only a few years since Mars entered into the sphere of our practical observations. I may add that only very few of the Earth’s inhabitants have seen it in all its details, one of the foremost of these being the astronomer Schiaparelli, the Director of the Milan Observatory.