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"It don't signify to you with your brilliant look-out, but as to myself, my guiding-star always is, 'Get hold of portable property.'" (24.41)
Wemmick is all about owning goods that can be moved quickly, so his concept of money is closely tied to mobility. He knows that wealth (in the vague stocks, land, and savings kind of way) can be appropriated and lost, and he doesn't care about having the "right" kind of money in land; he just wants to live comfortably and to be able to keep hold of his wealth.