Select the allusion in the passage. The engineer had listened to the enthusiastic sailor developing these imaginative
projects. To attack this mass of granite, even by mining, was a Herculean task, and
it was truly vexing that nature had not helped them in their necessity. But he
answered Pencroff, simply by proposing to examine the wall more attentively, from
the mouth of the river to the angle which ended it to the north.