Sentence:  With "Severne" she along doth go, / Her <WSD>Metamorphosis</WSD> to show ; / And makes the wand'ring "Wy" declaim / In honour of the "British" name.<!-- entire passage is in italics, and portions italicized here are in roman, in the edition linked --> 
Meaning of the word marked with <WSD> tags:  A transformation, such as one performed by magic.