"There grows upon the impatient imagination a building, a dome of crystal, across the translucent surface of which flushes of the most glorious and pure prismatic colours pass and fade and change. In the centre of this transparent chameleon-tinted dome is a circular white marble basin filled with some clear, mobile, amber liquid, and in this plunge and float strange beings. Are they birds? "They are the descendants of man--at dinner. Watch them as they hop on their hands--a method of progression advocated already by Bjornsen--about the pure white marble floor. Great hands they have, enormous brains, soft, liquid, soulful eyes. Their whole muscular system, their legs, their abdomens, are shrivelled to nothing, a dangling, degraded pendant to their minds." The further visions of the Professor are less alluring. "The animals and plants die away before men, except such as he preserves for his food or delight, or such as maintain a precarious footing about him as commensals and parasites. These vermin and pests must succumb sooner or later to his untiring inventiveness and incessantly growing discipline. When he learns (the chemists are doubtless getting towards the secret now) to do the work of chlorophyll without the plant, then his necessity for other animals and plants upon the earth will disappear. Sooner or later, where there is no power of resistance and no necessity, there comes extinction. In the last days man will be alone on the earth, and his food will be won by the chemist from the dead rocks and the sunlight. "And--one may learn the full reason in that explicit and painfully right book, the _Data of Ethics_--the irrational fellowship of man will give place to an intellectual co-operation, and emotion fall within the scheme of reason. Undoubtedly it is a long time yet, but a long time is nothing in the face of eternity, and every man who dares think of these things must look eternity in the face." Then the earth is ever radiating away heat into space, the Professor reminds us. And so at last comes a vision of earthly cherubim, hopping heads, great unemotional intelligences, and little hearts, fighting together perforce and fiercely against the cold that grips them tighter and tighter. For the world is cooling--slowly and inevitably it grows colder as the years roll by. "We must imagine these creatures," says the Professor, "in galleries and laboratories deep down in the bowels of the earth. The whole world will be snow-covered and piled with ice; all animals, all vegetation vanished, except this last branch of the tree of life. The last men have gone even deeper, following the diminishing heat of the planet, and vast metallic shafts and ventilators make way for the air they need."