Heating Help

Thanks to Thomas M. Long, P.E. for scanning and sharing this one. He writes, "I don't remember where I got this, because I've had it in a file for a number of years. The reason I kept it is because we lived in a duplex about 30 years ago that had one of these gravity furnaces, although it had been converted to burn fuel oil. This was the 'central' heating system and included a square cast iron grate in the living room floor. Somehow the warm air worked its way up the stairs and managed to keep at least part of the house reasonably warm."