Speculum mundi, or, A glass representing the face of the world [electronic resource] : shewing both that it did begin and must also end, the manner how, and the time when, being largely examined : the whole of which may be fitly called an hexameron, or discourse of the clauses, continuance, and qualities of things in nature : occasioned as matter pertinent to the work done in the six days of the worlds creation / by John Swan.