in 1684, there was a thatched cottage between East Porth and West Porth on Teän which belonged to a Mr. Nance who is reputed to have introduced kelp burning to Scilly. Kelp burning provides sodium carbonate for glass making and the practice continued in the islands until 1835. Kelp burning only produces 2-3 percent sodium carbonate and during the 19th century more efficient commercial and industrial methods ended the practice locally. Rights to areas of kelp were allocated to families and in 1787 Thomas Woodcock, his son and James Ashford (all of St Martin's) were accused of "having trespassed on his (Nance's) preserves". After the hearing, the court decided that the cutting of ore-weed and the making of kelp on Teän was the prescriptive right of Nance, and the trespassers were fined 2s 6d each. His family continued to live on Teän for several more generations and by 1717 there were ten people living on the island, but in 1752 William Borlase only saw fields of corn and ruined buildings.