Final answer:
Henry's interest on the beach is captured by the sight of a woman's dress, which leads him to express his excitement and recollect past memories.
Step-by-step explanation:
What catches Henry's interest on the beach seems to be a woman's dress that appears purple black in the shade. Henry, filled with emotion, takes off his hat, places his hand upon his heart, and starts to approach the figure, displaying signs of feverish excitement.
Unfortunately, there isn't enough context provided to pinpoint which Henry is being referenced or from which literary work this excerpt is taken.
Nevertheless, based on the description offered, we can infer that the dress or the woman associated with the dress is what captures Henry's attention and interest, leading him to act earnestly and passionately before Wil-iam intervenes by distracting him with a flower, at which point Henry's attention shifts to reminiscing about the forests of Uruguay and a beautiful companion from his past.