“One thing is certain, that the sun will finally lose its heat; it is condensing and contracting, and its fluidity is decreasing. The time will come when the circulation, which now supplies the photosphere, and makes the central mass a reservoir of radiant energy, will be obstructed and will slacken. The radiation of heat and light will then diminish, and vegetable and animal life will be more and more restricted to the earth’s equatorial regions. When this circulation shall have ceased, the brilliant photosphere will be replaced by a dark opaque crust which will prevent all luminous radiation. The sun will become a dark red ball, then a black one, and night will be perpetual. The moon, which shines only by reflection, will no longer illumine the lonely nights. Our planet will receive no light but that of the stars. The solar heat having vanished, the atmosphere will remain undisturbed, and an absolute calm, unbroken by any breath of air, will reign. “If the oceans still exist they will be frozen ones, no evaporation will form clouds, no rain will fall, no stream will flow. Perhaps, as has been observed in the case of stars on the eve of extinction, some last flare of the expiring torch, some accidental development of heat, due to the falling in of the sun’s crust, will give us back for a while the old-time sun, but this will only be the precursor of the end; and the earth, a dark ball, a frozen tomb, will continue to revolve about the black sun, travelling through an endless night and hurrying away with all the solar system into the abyss of space. _It is to the extinction of the sun that the earth will owe its death, twenty, perhaps forty million years hence._” The speaker ceased, and was about to leave the platform, when the director of the academy of fine arts begged to be heard: “Gentlemen,” he said, from his chair, “if I have understood rightly, the end of the world will in any case result from cold, and only several million years hence. If, then, a painter should endeavor to represent the last day, he ought to shroud the earth in ice, and cover it with skeletons.” [Illustration: A WORLD OF ICE. ] “Not exactly,” replied the Columbian chancellor. “It is not cold which produces glaciers,—it is _heat_. “If the sun did not evaporate the sea water there would be no clouds, and but for the sun there would be no wind. For the formation of glaciers a sun is necessary, to vaporize the water and to transport it in clouds and then to condense it. Every kilogram of vapor formed represents a quantity of solar heat sufficient to raise five kilograms of cast-iron to its fusing point (110°). By lessening the intensity of the sun’s action we exhaust the glacier supply.