Sentence:  Now one of the most engrossing questions in the politics of the State arises from the filling of the rivers and the destruction of the agricultural lands by the debris from these hydraulic mines. A dam on the Feather River, near Marysville, was authorized by the Legislature, and after the expenditure of half a million dollars its success is questioned, and "<WSD>slickem</WSD>" continues to muddy at least the political waters. 
Meaning of the word marked with <WSD> tags:  A very fine waste material produced by hydraulic mining which tends to contaminate waterways.