to enable the beats of the Adelaide sidereal clock to be used as a control on the rate of the chronometer used for the boundary observation. After these initial tests a comprehensive program was then arranged for the second stage of the border determinations, which were to take place during the following year and dates were then set for that to happen, from 20 April to 10 May 1921. Deakin Pillar One of the concrete piers mentioned, which were cubic concrete blocks slightly smaller than , would later be named as the Deakin Pillar (1921), being from where the larger border marker, the Deakin Obelisk (1926), would be set out from. Deakin Obelisk The Deakin Pillar is approximately west of the Deakin Obelisk. The Deakin Obelisk was erected as closely as was possible with the technology of 1926 to 129° east. The Deakin Obelisk has a copper plug embedded into the top centre of the concrete obelisk, which determines, on the ground, the South Australian border with Western Australia by a line drawn south to the coastline of the Great Australian Bight and north through this point to 26° south. WA/NT border marking history Shortly after the 1921 determinations of the border of South Australia and Western Australia, the Government Astronomer for South Australia, G.F. Dodwell and the Government Astronomer of Western Australia, H.B. Curlewis and party travelled by the State Ship Bambra to the port of Wyndham, Western Australia. From Wyndham they were guided by Michael Patrick ("M.P.") Durack to a point he perceived as the northern boundary between his Argyle Downs Station and Jack Kilfoyle's Rosewood Station, which was also Western Australia's border with the Northern Territory or 129° east. Most of Rosewood station is in the Northern Territory but some distance further south Rosewood also extends into the East Kimberley Region of Western Australia. From the chosen position, two concrete pillars were erected similar to those described above and portable radio masts set up, before the determinations were carried out by the scientists using the same methods of wireless time signals as were used at Deakin. Austral Pillar One of the concrete pillars erected, which was the one used as the point of the determinations, was marked by the expedition party to show how far east of Greenwich they were in hours, minutes and seconds, and became known as the Austral Pillar. The Austral Pillar, the point