The Saugus Iron Works, in Saugus, Mass. (about 20 miles north of Boston)
The Blast Furnace
Saugus' blast furnace was powered by a large overshot waterwheel to pump the bellows. Left and above you can see a scale model showing the waterwheel under the charging bridge and then from the other side of the furnace, the bellows underneath the sloping shed roof.
To the right, a view from the charging bridge today, looking down on the waterwheel of the furnace, and with a view of the waterwheels of the forge in the distance.
Here two views of the furnace's tapping arch, where the molten iron was
tapped from the furnace onto the hearth. At left is a view of the arch today
and to the right in a diorama as it would have appeared back when the hearth
was functioning.
The Saugus furnace worked like all medieval and early modern furnaces -
loads of iron ore, charcoal, and often a calcium-based flux (crushed limestone
or oyster shells were common) were alternately poured in the top of the stack.
As the charcoal burned, urged on on by the bellows (the modern frame of which
is being rebuilt at right), the furnace temperature rose to over 1400˚C and
the iron melted and flowed to the bottom (seen in the cross-sectional diorama
at right). For more information on the iron-making process, see our one-minute-lesson
on the chemistry of iron. 
to
the right, you can see the giant axle of the waterwheel whose cams (the small
wooden protrusion seen here on top) rotated around massaging the back end
of the bellows. The cam arrangement can also be seen driving the massive
triphammers in the forge,on the following page. 
