If we have brothers living on Jupiter, they must be about the size of ants.
If, indeed, we go down to the bottom of the matter, we shall be forced to admit that there is, in a being capable of observing and discerning, something permanent, fixed, and superior to spatial dimensions, and independent of their variations. This something is the feeling of the required effort, of the executed movement, and the fatigue that follows it. The feeling appertains essentially to every muscle that works under the impulsion of the will. This feeling is neither line, nor surface, nor volume, nor weight. It is the same for small and large animals, for the child and the man, the dwarf and the giant. He who lifts the heaviest weight he can manage fatigues himself always just so much, whether he be weak or strong, fresh and nimble or tired and dull, sturdy or feeble. The ant dragging a straw experiences integrally the same feeling as the porter carrying a sack, or the horse pulling a wagon, if the straw, the sack, and the wagon are proportioned to the strength of the ant, the man, and the horse.
Magamicros, transported to Mars, has retained in himself the inner unity of measure that permits him to estimate masses according to his strength. When on the earth he lifts loads of fifty kilogrammes greatest weight, the equivalent of this weight on Mars is not for him fifty Martian kilogrammes, but two hundred kilogrammes greatest weight. Hence his astonishment. I say, purposely, sometimes weight and sometimes mass. Fundamentally, he estimates weight; but weight represents to him a certain quantity of matter as related to his strength and his requirements. No matter if the kilogramme of Mars is only equivalent to one sixteenth of the kilogramme of the earth. If a Martian kilogramme of meat, bread, or beans represents on Mars the same relative amount of work or pleasure as the earthly kilogramme of meat, bread, or beans does on the earth, it is equivalent, even equal to it; but if Megamicros does not find in it the same quality of restoring strength or producing pleasure, he will think it is different.
Pleasure, pain, and fatigue are not measured by the metre, litre, or kilogramme. The pleasure felt by a grasshopper in eating a blade of grass is not less than that of a cow with the range of a whole pasture. But we know that the grasshopper has a more pressing need of food than the cow, because it is smaller. If, then, by an ideal reduction of proportions, the cow fails to get the same satisfaction out of the meadow, she will not judge its size by sight, but by her stomach.
Let us go still further. None of my readers has thought of raising the objection that while transporting Megamicros to Mars
