High on the sun-scorched hillside above the steamy littoral of the Caribbean Sea the Spanish-Indian town of Rio Frio lay sweltering in the heat of afternoon. The flat-topped, white houses surrounding the plaza reflected a dazzling glare, and the heat shimmered mercilessly upon the rough paving-stones. Flakes of plaster had fallen from the buildings; a few of them were mere ruins, relics of a past age; for the town had been built when conquistadores...