I learned, however, that day once for all that both Summerlee and Challenger possessed that highest type of bravery, the bravery of the scientific mind. Theirs was the spirit which upheld Darwin among the gauchos of the Argentine or Wallace among the head-hunters of Malaya. It is decreed by a merciful Nature that the human brain cannot think of two things simultaneously, so that if it be steeped in curiosity as to science it has no room for merely personal considerations.
