Detholiad o Morris, L., 1748. Plans of Harbours, Bars, Bays and Roads in St. George's Channel. Mae'r detholiad (tudalen 42) yn disgrifio'r defnydd a wneir o wymon, neu fôr-wiail, o fewn y diwydiant lleol yng Nghaergybi.
Mae'r detholiad yn darllen fel a ganlyn: ”Here is a Plant growing on the Sea Rocks, called by the natives Gwymmon, (in English Tang) of which they make great profit, by burning it into a Kind of Salt, called KELP; one of the Ingredients in making Glass, and used also in Allum Works.”