That is inevitable.

Henry's tender patience with Sylvia's moods and unreason made him see over her character, as he could see over her physical head.

Lately this sense of mystery had increased, in a way, his comprehension of his own stature.

The more mysterious Sylvia became, and the more Henry's patience was called into action, the taller he appeared to himself to become.
While he had been getting the corn out in the garden, and preparing it to be cooked, he had reflected upon Sylvia's unaccountable emotion and her assertion that there was no reason for it, and he realized his masculine height.

He knew that it would have been impossible for him to lose control of himself and then declare that there was no cause; to sway like a reed driven by the wind.
Henry was rather taken by this idea.