An extract from Morris, L., 1748. Plans of Harbours, Bars, Bays and Roads in St. George's Channel. The extract (page 42) describes the use of kelp in local industry at Holyhead.

The extract reads as follows: ”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.”