Gunfleet, Middle and Buxey sands, and by beacons on the Whitaker, Shoe and Blacktail spits. A buoy marked the easternmost point of the Nore sandbank at this time, and three more buoys marked sandbanks in the middle part of the estuary (Spaniard, Red Sand and the Oaze). The Nore Lightship, the world's first lightvessel, was established in the Estuary as a private venture in 1732 to mark the 'best position for entering the Thames and Medway, and to clear the Nore Sand'. The coastwise approach from the north was aided by the establishment of the Sunk lightvessel in 1802 'to mark the north-east entrance to East Swin, and to guide vessels round Long Sand'. Later, the Swin channel was further marked by lightvessels at Swin Middle (1837) and Mouse (1838), and by screw-pile lighthouses on the Maplin Sands (1841) and at Gunfleet (1856). Meanwhile, one of the outlying sandbanks of the Estuary was marked by a lightvessel at Kentish Knock (in 1840); and in due course the southern approach was marked by lightvessels at the Tongue (1847) and Girdler (1848) sands, with another being added (between these two) in the Princes Channel (1856). In 1851 two more screw-pile lighthouses were built further upriver, on the northern foreshore of Sea Reach: at Mucking and on the Chapman sands (just off Canvey Island). Prior to 1684 beacons were set up on the mudflats north of the Swin channel, to help vessels approaching the Thames from the north to navigate the sands. Pan-sand Beacon was set up by Trinity House in 1774 to mark a dangerous sandbank on the southern approach. Similar daymarks were set up on other nearby sandbanks in later years, including on Margate Hook (1843), Middle Ground (1844) and Shingles (1846). Trinity House also maintained beacons further upriver, including at Broadness (established in 1821), Stoneness (1839), Erith (1830) and Tripcock (1832). In 1864 responsibility for maintaining the navigation lights of the River Thames between London Bridge and Yantlet was transferred by Act of Parliament from the Thames Conservancy to the Corporation of Trinity House; responsibility for buoyage was transferred likewise in 1878. In 1885 the beacons at Broadness and Stoneness were replaced with iron-frame experimental lighthouses, each lit by a novel system which would allow the light to function unattended (except for a twice-weekly visit by a boatman for cleaning and maintenance). Broadness was lit by Pintsch gas, and Stoneness