Harriott married, and after trying his hand at underwriting and the wine trade, settled down as a farmer at his native place in Essex. In 1781–2 he reclaimed from the sea
Rushley Island of two hundred acres, between
Great Wakering and
Foulness, which had several feet of water on it at spring-tides, by enclosing it with an embankment three miles in length. He then erected farm-buildings and sank wells on it. For this project the
Society of Arts awarded him a gold medal; also a prize for an improved road harrow for levelling ruts. Harriott at this time was a surveyor of roads and an Essex magistrate as well as a farmer. In 1790 the destruction of his farm by fire brought Harriott to the verge of ruin. He called a meeting of his creditors, who behaved well; emigrated with his family to the United States, where he remained in an unsettled position for some years, and then returned home again in 1795. On 31 October 1797 Harriott, then described as of Prescott Street,
Goodman's Fields, in the county of Middlesex, patented an improvement in ships' pumps, which was adopted in the navy, and set up a small factory. He subscribed to
William Pitt's loyalty loan, and suggested improvements in the organisation of volunteer corps and sea and river
fencibles. ==Law enforcement in the Port of London==