Thanks for re-posting the tunnel link. I don't know how modern day flows compare to the past but if similar it's amazing how industry flourished on such a small stream in dry spells. There would have been much more water at times as is evidenced by the clearance given by building on the flood plain before the stream was sunk inside a culvert which must have been lower. There was a shortage of water for industry before the steam engine was developed. This shortage and inconsistancy was the reason that Astn Furnace changed over to a Newcomen steam engine to power the furnace bellows. When the furnace became a wire mill I wonder if the Newcomen engine was upgraded to a Watt engine. The two concerns were close together. Perhaps the Newcomen foundations were modified and reused. Anyway, the photo's put an end to theories about there being crocodiles below the works in Porchester Street Nary a sighting.