See another reference to the recovery of his cattle, and the unearthing of the thief Cacus, by Hercules, at p. 155, 1. 4.
It is not very easy to see the application of the satire here; but probably Swift purposely confuses the reminiscences of the labours of Hercules so as to mark the mock-heroic labours of the True Critic. Errors (which had better be left in their obscurity) the Critic drags out, as the hero did Cacus ; these errors he multiplies, — as the Hydra's heads were multiplied on Hercules' hands ; then, instead of clearing the Augean stable, as the hero did, by making streams flow through it, he heaps up and preserves the dung ; and lastly, as Hercules drove away the brazen-clawed birds of the Stymphalian lake, so the Critic would discourage those whose taste guides them to browse upon what is of real value in the Tree of Knowledge. The Critic reverses, rather than emulates, the labours of Hercules. But, from p. 128, 1. 17, it would seem as if the Critic himself performed the function of the Stymphalian birds.