(or fifteen thousand pounds), and elephants should move mountains. We can not dispute the accuracy of the experiments or the calculations, nor impeach the sincerity or judgment of the experimenter. The facts are, moreover, conformable to observations. A caterpillar in the closed hand will make prodigious efforts to open his prison; and who has not seen ants carrying things three or four times as large as themselves? Various attempts have been made to escape the consequences that were deduced from these experiments, but they still stand, apparently defying criticism. Must we, then, resign ourselves to being a hundred or two hundred times weaker than a beetle? Are insects really, in physical force, kings of creation?
Not yet. An important element has been neglected. No account has been made yet of the time it takes the insect to perform its wonderful feat. Whenever we raise a given weight to any height, by whatever method, the labor performed is in proportion to the weight multiplied by the height; and this product always gives the measure of that labor. The same product, under certain restrictions, furnishes the measure of the force that is utilized in the work. A dog is not as strong as a horse, but both animals expend precisely the same force in raising a kilogramme a metre. Whatever the kind of work he may wish to calculate, even though it be horizontal, it is always reducible to the elevation of a certain weight to a certain height, and is in practice measured by a formula of which these are the terms.
While, however, the quantity of force that must be expended for a determined work is invariable, this is not the case with the manner in which that expenditure may be distributed. If I wish to strike a single strong blow, I execute a quick movement. If my muscular power is weak, I must have more time. It is possible, then, for time to supply a deficiency of power. I can make such a substitution applicable in two ways, by dividing the resistance, or by using a machine as a lever, which, when everything about it is considered, is nothing more or less than a device by means of which we replace power with time.
Accurately to compare the strength of a May-bug with that of a man, we must take into the account the time which the insect requires to perform the work exacted of it. Suppose a horse harnessed to a load of half his weight, and a May-bug drawing a tray fifty times as heavy as itself: the beetle's load will be relatively a hundred times as heavy as the horse's. But if the horse needs only a second to raise his load a metre, while the insect takes a hundred times as Ions; to produce the same effect, then the efforts of which they are both capable are proportionably the same. The case is the same, only the appearance is changed, when the force is spent in maintaining the weight at an equilibrium.
In a similar manner we may account for the power manifested by the insect which I cover with a board a hundred times as heavy as itself, and which gets its head under the edge, raises it, and escapes.