Classicly

Nobody had ever been able to climb to the summit of that precipitous height, and when the Bird boys landed there once from their aeroplane and planted a flag above the nest of the white-headed eagles they achieved a great triumph. The incident to which Elephant alluded had been brought about during a sudden thunder storm that had caught the rival aeroplanes while making a flight to the top of the mountain; and at that time the Bird boys were indeed placed in a position to save the lives of Percy Carberry and his comrade Sandy; but since gratitude was a foreign element in the make-up of the jealous rival, he had never shown that he meant to change his tactics toward Frank and Andy.