7 68 THE POPULAR SCIENCE MONTHLY. 



way in which we can weigh and measure, submit the results to cal- 

 culation, and draw from them conclusions which are formally quite 

 legitimate, and still be all the time on the wrong track ; then examine 

 how we may be set upon the right road, and led to a new conclusion 

 more plausible and more in harmony with the rest of our knowledge. 



It has been discovered that the flea can leap two hundred times its 

 length. Our admiration at this is changed to astonishment when it is 

 demonstrated by calculation that, if nature had endowed the horse 

 with a degree of strength similarly proportioned to his weight he 

 would have been able to clear the Rocky Mountains at a bound, and 

 that with a like effort a whale would be able to leap to a height of 

 two hundred leagues. What can be more unassailable than these 

 conclusions, founded on weight, measure, and calculation ? 



It is true that, if, instead of comparing the weights of the horse 

 and the flea, we had compared their heights, we should have found 

 that the horse's leap would not measure more than three hundred me- 

 tres. Why is preference given to the weight ? Because it is its whole 

 body with its three dimensions and its density that the flea hurls to two 

 hundred times its height, and it is the same feat of strength that we 

 demand in vain of the horse. Calculations have also been made to 

 show that, if a man could move with a speed proportioned to that of 

 certain insects, he would be able to travel more than ten leagues in a 

 minute, or sixty times as fast as a railroad-train. 



The Amazon ants, going to battle, travel from two to two and a 

 half metres a minute. The Amazons of antiquity, to be even with 

 them, if we judge by the relative heights, should have traveled eight 

 leagues an hour. We have, however, in this case, to compare the 

 forces with which given masses move themselves, and should take ac- 

 count of weights or volumes. If we proceed by this rule, we shall 

 obtain formidable numbers, that stagger the boldest imagination. The 

 warlike inhabitants of the banks of the Thermodon would have to get 

 over fifty thousand leagues in an hour. Yet, who can deny the truth 

 of the observations, the rigor of the measurements, or the justice of 

 the reasoning ? 



The authors of these interesting calculations have not had in mind 

 only to make known some figures of comparison, good to store up, even 

 if they are never used, but they have endeavored to set forth the idea 

 that certain insects are much better endowed with powers of leaping 

 and speed than the vertebrates, and especially than man. The per- 

 sons who express this conclusion have failed to conform to the precept 

 that they must not extract more from their facts than is rigorously 

 contained in them, and are the victims of a scientific illusion, which is 

 quite wide-spread, but not hard to dissipate. What is in question ? 

 It is the valuation of the labor necessary to raise a certain weight 

 to a certain height. The labor increases in proportion to the weight 

 and the height. When, then, two animals of different masses leap to 



