How could he know why they fought?
White men have no reason when they are like that.
Just as Lingard was beginning to fear that he would be unable to restrain much longer the violence of the younger man, he felt Willems' muscles relaxing, and took advantage of this opportunity to pin him, by a last effort, to the rail.

They both panted heavily, speechless, their faces very close.
"All right," muttered Willems at last.

"Don't break my back over this infernal rail.

I will be quiet." "Now you are reasonable," said Lingard, much relieved.

"What made you fly into that passion ?" he asked, leading him back to the end of the jetty, and, still holding him prudently with one hand, he fumbled with the other for his whistle and blew a shrill and prolonged blast.