And what is this ether? Is it matter in some subtle form, or is it something else? We do not know; certainly it is no form of matter known to us, and its reality has even been called into question of late. Hæckel, as we know, contended (“The Riddle of the Universe”) that the ether must be like some extremely attenuated jelly, and that a sphere of it the size of the earth would probably weigh about 250 pounds! Such crude conceptions have long since been given up. It is far more subtle than this. Is it analogous to the finest gas? Some have thought so; and yet Sir Oliver Lodge, one of the greatest authorities upon the ether, has contended that it is more dense and solid than platinum or gold, and that matter represents mere “bubbles” within this dense medium, capable of moving freely through it. In support of this view, he has cited (in his “Ether of Space”) the enormous gravitational pull of the earth upon the moon, _e. g._, or of the sun upon the earth. The mass of the earth is approximately 6,000 trillion tons; that of the moon one-eightieth of this. From these data, the gravitational pull of the earth upon the moon can be calculated; and, regarding this, Sir Oliver says: “A pillar of steel which could transmit this force, provided it could sustain a tension of 40 tons to the square inch, would have a diameter of about 400 miles.... If this force were to be transmitted by a forest of weightless pillars, each a square foot in cross section, with a tension of 30 tons to the square inch throughout, there would have to be 5 million million of them.” Calculating the gravitational pull of the sun on the earth, in a similar manner, it was calculated that the strain in this case would have to be borne by “a million million round rods or pillars each thirty feet in diameter.” It may readily be seen, then, from these figures, that something enormously dense, apparently, must exist in order to bear this strain, and this must be the ether. And yet no physical experiments have proved to us the existence of the ether; we only infer its presence, and say that it _must_ exist, in order to account for certain phenomena observed in physics. It was, I think, Lord Kelvin who remarked that no man could believe in the ether without at the same time believing it to possess opposite and contradictory properties! Indeed, it would seem so! CHEMISTRY AND META-PHYSICS