Note 365 — Chapter VI · THE PROTO-SIDERIC OR EARLY IRON AGE OF WEAPONS.
Reading edition
Colonel Yule (M. Polo, ii. 96) remarks that in the Middle Ages steel was regarded as a distinct natural species made of another ore, and relates how a native to whom an English officer had explained the process of tempering replied, ‘What, would you have me believe that if I put an ass into the furnace it will come out a horse?’