686 POPULAR SCIENCE MONTHLY. 



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 kilo- 

 grammes greatest weight, the equivalent of this weight on Mars is 

 not for him fifty Martian kilogrammes, but two hundred kilo- 

 grammes greatest weight. Hence his astonishment. I say, pur- 

 posely, 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. JSTo 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 



