Sentence:  The best tough soft iron, such as will weld round, is drawn into rods by smiths, using charcoal fires, and taking welding heats every time, the rod is about 1.4 inch diameter, 9 or 10 feet long, containing 4lbs. each, tapered at each end to a long point; they are first <WSD>anealed</WSD> by being brought to a bright red heat, in a furnace excluding the air as much as possible, for if the air can be entirely excluded, no scab will rise in anealing; ... 
Meaning of the word marked with <WSD> tags:  To subject to great heat and then (often slow) cooling, and sometimes reheating and further cooling, for the purpose of rendering less brittle; to temper; to toughen.