Sentence:  When they cross any great Water, or violent <WSD>Fresh</WSD>, or Torrent, they throw Tobacco, Puccoon, Peak, or some other valuable thing, that they happen to have about there, to intreat the Spirit presiding there, to grant them a safe passage. It is call'd a <WSD>Fresh</WSD>, when after very great Rains, or (as we suppose) after a great Thaw of the Snow and Ice lying upon the Mountains Page 43 to the North West, the Water descends, in such abundance into the Rivers, that they overflow the Banks which bound their Streams at other times. 
Meaning of the word marked with <WSD> tags:  The mingling of fresh water with salt in rivers or bays, as by means of a flood of fresh water flowing toward or into the sea.