This is from Alfred G. King's 1923 text, 500 Plain Answers to Direct Questions on Steam, Hot Water, Vapor and Vacuum Heating.
Heating Museum → Greenhouse Heat Help Topics
Take a stroll through HVAC history in our Heating Museum. This section of our website preserves history and answers that so-important question: What the heck is that thing? Whenever you run across anything unusual, chances are you’ll find the old literature about it right here.