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.