Australia from Surveys made by order of the British Government Combined with those of D’Entrecasteaux, Baudin, Freycinet &c.&c.

Arrowsmith’s important pair of maps of Australia on two sheets, recording the extent of settlement and the progress of inland exploration up to 1850.

Arrowsmith cleverly issued these maps so that they could be sold either as single sheets or joined as one map. 

Each sheet is printed with a separate title, the left sheet has a large generic title referring to the entire continent while the right sheet has been given a much more specific and smaller title. In this way both sheets could be trimmed at the 134th meridian east, where Arrowsmith added ‘joining line‘ to both maps but on opposite sides of the meridian. Additionally, only the right sheet has been update with inland information for South Australia, which would be retained when joined.

Twenty-six counties are shown in Western Australia, numbered and listed in the table at lower left. The results of John Septimus Roe’s 1848-1849 explorations, south and east of Perth, south coast as far east as the Russell Range and north to 32°30’S, then north and west back to Perth, have been added to this issue. Of all the maps which Arrowsmith published of Australia, this one records the most change, particularly in the south-eastern part of the map which was the area that had the most economic interest for farming. The
routes of John Edward Eyre 1839-1840, Paul Edmond Strzelecki 1840,
Ludwig Leichhardt 1844-45, Thomas Livingstone Mitchell 1845-47, Edmund
Besley Court Kennedy 1847-1848.

The depiction of the South Australia/Western Australia boundary becomes significant from this 1850 issue onwards. Twenty-one states of the east sheet have been seen and there may be more.  

References:

Prescott 1850/1, Tooley 85, p.14