Sentence:  By some means or other the water flows <WSD>purely</WSD>, and separated from the filth, in a deeper and narrower course on one side of the rock, and the refuse of the dirt and troubled water goes off on the other in a broader current [...]. 
Meaning of the word marked with <WSD> tags:  Without physical adulterants; refinedly, with no admixture. (from 16th c.)