greater elevation. Its position, according to HMS Beagle, is lat. 32d 0m 14s South, long. 115d 26m 6s East." Original tower Stokes returned to Fremantle on Beagle in April 1843 and wrote: "In the forenoon of the 23rd we saw the lighthouse of Rottenest ; and regarded it with great interest, as the work of the aborigines imprisoned at the island." Rottnest had been used as a prison for Aboriginal people since 1838. Superintendent of Public Works Henry Trigg designed the first lighthouse and laid the foundation stone in January 1842. Perth builder Bayley Maycock oversaw construction of the tower at a cost of £500 and used labour provided by the prisoners and locally quarried limestone. Construction seemed to be quite protracted for reasons which are unclear—possibly because of resistance by the Prisoner's Superintendent Henry Vincent, who disliked outside meddling on the island. The first keeper, Samuel Thomas, was appointed on 18 January 1849—two years before the light was lit. Thomas's duties initially included operating a system of signalling using flags and flares to indicate the arrival of ships. Different signals and flag combinations indicated ships to the north or south of the island and these were monitored from a pilot's lookout at Bathurst Point on the north-eastern extremity of the island and then relayed to Arthur Head at Fremantle. Four flagpoles were built at the lighthouse for signalling. The flags were about square. When confirmation of a ship's arrival was received, the lookout man at Arthur Head raised a blue flag for the information of Fremantle residents. Vincent wrote to Colonial Secretary Henry Revett Bland on 25 August 1849, that "... the Tower of the Litehous is all finesh...". The conclusion of construction coincided with the closure of the island prison establishment and the removal of inmates back to the mainland. The Aboriginal prison population did return however, between 1855 and 1931. The tower's completed height was shorter than the design, and commissioning was finally completed in 1851 when the revolving lamp and clockwork mechanism were fitted. Unusually for the period, as most lighthouse lamps and mechanisms came from England, the machinery for the revolving catoptric light was designed and built in Fremantle. Assistant Surveyor-General Augustus Gregory designed the mechanism which comprised two sets of three oil-burning lamps, each with a silvered parabolic reflector. In 1850, a contract was let to Alfred Carson to construct the revolving apparatus at