Sentence:  The road is winding, and consists of a succession of short, steep descents, diversified by occasional sloughs, which might well be called "<WSD>sloughs of despond</WSD>," into one of which Manuel was thrown rather unceremoniously, by the bursting of his saddle-girths at the top of one of these short hills, by which means he took a flight over the head of his beast, and found a soft resting place in the mud at the bottom. 
Meaning of the word marked with <WSD> tags:  A dreary bog or marsh.