Sentence:  Let us weigh the promises of the one and of the other in the balance of truth, and we shall finde that the promises of God are "gold", and the promises of the devil are "Alchimy", such which though they glitter much, have no worth or excellency in them. ... God's, are substantial realities, and his, vanishing and fleeting shadows windy and swollen bladders, which but a little prickt, do quickly fall and grow <WSD>lank</WSD>. 
Meaning of the word marked with <WSD> tags:  Languid; drooping, slack.