If—and the thing is wildly possible—the charge of writing nonsense were ever brought against the author of this brief but instructive poem, it would be based, I feel convinced, on the line (in p. 144)

In view of this painful possibility, I will not (as I might) appeal indignantly to my other writings as a proof that I am incapable of such a deed: I will not (as I might) point to the strong moral purpose of this poem itself, to the arithmetical principles so cautiously inculcated in it, or to its noble teachings in Natural History—I will take the more prosaic course of simply explaining how it happened.