<a href="https://en.wikipedia.org/wiki/Blast_furnace" class="extiw" title="en:Blast furnace">Blast furnaces</a> <a href="https://en.wikipedia.org/wiki/Pig_iron" class="extiw" title="en:Pig iron">Pig iron</a> bed at Port Clarence Works, Middlesborough, County Durham, England
<a href="//commons.wikimedia.org/wiki/User:Borvan53" title="User:Borvan53">Borvan53</a>
<a rel="nofollow" class="external text" href="https://archive.org/details/principlespracti00macfrich">California Digital Library</a>