Sentence:  [A]s he [the Devil] is the Prince of the Power of the Air, taking the Air there for "the Elementary World", how eaſily could he, <WSD>at one Blaſt</WSD>, ſweep all the Surface of the Earth into the Sea, or drive weighty immenſe Surges of the Ocean over the whole Plane of the Earth, and deluge the Globe at once with a Storm? 
Meaning of the word marked with <WSD> tags:  At once, at the same moment in time. (from 1379)