Sentence:  ... conveyancing of property to a background of ships loading or discharging and the clanging of wharf cranes, but in August, when the tide was low, the River Lyle's gum-like, perspiring mud banks released a <WSD>mephitis</WSD> ... 
Meaning of the word marked with <WSD> tags:  A poisonous or foul-smelling gas, especially as emitted from the earth; an unpleasant (smell).