The large empty spaces are traversed by red lines, principally to the south-west, marking "country which has been lately walked over." The red lines end abruptly on the far side of a curve in the course of the river Nepean, where swamps and hills are shown.

The map-maker "saw a bull" near a hill which was called Mount Hunter, and marked it down.
West of the settlement, behind Richmond Hill on the Hawkesbury, the map indicated a mountain range.

Bass's first effort at independent exploration was an endeavour to find a pass through these mountains.

The need was seen to be imminent.

As the colony grew, the limits of occupation would press up to the foot of this blue range, which, with its precipitous walls, its alluring openings leading to stark faces of rock, its sharp ridges breaking to sheer ravines, its dense scrub and timber, defied the energies of successive explorers.