‘May Heav’n protect our home from flame’ begins a prayer in the Servant’s Passage @nt_erddig. According to adverts of the time, these fire extinguisher grenades were designed to be hurled into the flames. The mixture of water, salt and chemicals inside would boil and produce fumes that could smother the fire... ...at least in theory - many weren't effective in practice. Discover more forgotten gadgets and eclectic items in our book, 100 Curiosities and Inventions. #NationalTrust