Mrs Gould's watercolor is an important recurring symbol of the lost innocence of the mine before development (and by extension, the innocence of the Goulds' early idealism). But it is also significant that here, it's introduced as part of the roster of symbols of conquest -- the guns, sabre and silver. The inference is that Mrs Gould's altruism, though opposed to progress, is nevertheless a dream-ideal itself, with its own desire of conquest.