But this difficulty in the way of flight through the ether was but slight as against the other defect that their systems had in common with all terrene bodies. They could develop heat easily enough; but how were they to keep intact and consistent in a vacuum constitutions which had been developed under the pressure of an atmosphere? How would the tissues and the organs of their bodies adjust themselves to the absence of atmospheric conditions? As they rose above the clouds, they had long felt as if their limbs and even the molecules of their bodies were without due subordination and apt to assume individual independence, even when the spirit grew boldest and most concentrated in its energy. Their own wings and faleenas that were intended for upper and rarer altitudes had to be made tougher and more elastic than for common flight close to the earth. They had to make them at last in a vacuum, and subject them to all the conditions that met them in the ether. But it would take myriads of generations, if not of geological ages, to bring their own bodies into such a state as to bear vacuum around them for years; and then in their terrene life with such a new constitution they would be unable to endure so great a pressure as that of the atmosphere near the earth. The only contrivance that seemed feasible was a farfaleena enclosing the traveller round, large enough to hold alfarene supplies for the long voyage, and strong enough to stand the pressure of an atmosphere within it. This they might manage after some years of experimentation. But enclosure within such a narrow space for so long a period, without the possibility of free movement into the ether, did not attract them; and any little accident in their machinery or to their supplies might make their faleena their tomb. Some other line must be taken by investigation and invention, if stellar migration was to become a possible and desirable thing.