Air Flow Rate Question

Well lads,

I am trying to spec a bellows for a type of forge and the only reference to it I have is from an old book saying the air pressure needs to be at least "25 pounds to the superficial foot" with the option of increasing that. Now I have looked up the term "superficial foot" and it seems to refer to a measurement for timber - a square foot of timber one inch thick. Would anyone here be able to convert this to a more modern value? The term superficial foot may refer to a cubic foot but I am not sure as it is a pretty old book.

If anyone could shed some light on this it would be greatly appreciated.

Also if anyone is interested, the piece in the book is referring to a horse shoe nail maker in Dublin in 1864 who would first heat up the nail rod as normal in his everyday forge. After it came to a red heat it would be placed over the anvil and a very strong blast of cold air applied to it. This apparently INCREASED the heat of the nail as there was so much friction from the air. The author goes on to say that this could be compared to an "aerolith" at rest. "The air from the bellows moving past it the same velocity with which an aerolith in motion would, under ordinary circumstances, travel through the lower region of the atmosphere."

Thanks for reading.