[jmclnx]

Ever see radiator in action ? The ones I have uses steam. Water would boil in the furnace and pressure would force the steam up to the radiators. Then the steam would condense, heating the apartment and the water would flow back down to the furnace to be re-heated again.

In the old furnace, every so often you would have to add water, depending on how cold it is outside.

The house was build over 110 years ago, so electricity was not too common back then. I probably think the source of heat back then was a coal furnace.