Sentence:  "Not forged!" and snatching Perth's levelled iron from the crotch, Ahab held it out, exclaiming &mdash; "Look ye, Nantucketer; here in this hand I hold his death! <WSD>Tempered</WSD> in blood, and <WSD>tempered</WSD> by lightning are these barbs; and I swear to temper them triply in that hot place behind the fin, where the white whale most feels his accursed life!" 
Meaning of the word marked with <WSD> tags:  Pertaining to the metallurgical process for finishing metals.