The Aztec Treasure-House by Thomas A. Janvier

By the winding way which we followed along the mountain-top (and that this was the way we wished to follow the King's symbol and the pointing arrow plainly showed), we came presently close beside the rift in the cliffs through which the waters of the upper lake had been discharged upon the city in the valley below and so had buried it. And here we made a very surprising discovery -- which was no less than that the great rift in the rocks through which the water had been let loose was not, as we had supposed, the result of some fierce convulsion of nature, but very plainly was the fiercer work of man. Along the face of the opening whence the water had poured forth the rock was grooved, showing that drill-holes had been made, close together, from the edge of the cliff backward to the lake that once had filled all the valley now lying bare and empty before us; and with the field-glass we could see that there was a like channelling of the rock upon the farther side of the break. And all doubt in our minds in regard to this matter was removed by our finding a vastly long drill -- made of the bright, hard metal that we now were familiar with, yet could not at all understand its composition -- lying close beside the chasm upon the bare rock.

"There has been the devil's own work here! " said Rayburn, as he fully took in this extraordinary situation. "Whoever did this must have spent months over it, perhaps years, working with such tools as these. They evidently went at it systematically, with the deliberate intention of drowning the whole crowd down below. From an engineering stand-point I must say that it's a good piece of work. See how cleverly they've picked out this particular spot, where the wall of rock went down almost perpendicularly into the lake, and so got the full value of the thrust of the water when their cuts were finished. If I'm not mistaken, there was a third line of drill-holes sunk in the middle of the mass that they meant to cut loose. That's the way I should have done it: then there would have been a little giving in the centre that would have helped to loosen the sides. But what a lot of incarnate devils they must have been to go at such a job!"