Warren Brown sets off to retrace the steps of Blaxland, Wentworth and Lawson as they journeyed across the Blue Mountains. HAVING made it to Katoomba yesterday I had a yarn with Robert Bettington, a 40-year-old Blue Mountains arborist whose most impressive tree is his family's. Robert is Lieutenant William Lawson's great-great-great-great-grandson and is preparing to take part in the upcoming bicentennial re-enactment to cross the mountains in May. Robert is very much in awe of his ancestor's achievement 200 years ago: "It was such a massive thing for Australia - these blokes just got in there and did it." In late May 1813, with no maps, no directions and no idea what lay beyond the mountains, Blaxland, Lawson, Wentworth, their Aboriginal guide, three convicts, four horses and five dogs were pressing further westward into dense, harsh scrub. Long days chopping through the bush and marking trees. For all their bearing-taking and compass-marching, this was an imprecise method of navigation and location. At times it must have seemed the wisest course of action would be to call it quits and turn back and - after all - what would been the shame? For the previous 25 years many had tried to cross this mountain range and failed. Besides - how far west would the enormous serrated sandstone plateaus they'd been traversing for nearly three weeks extend? The further away from civilization they went the less the chances of them returning alive. There was always the niggling question as to what they might find if they reached the other side. Was there viable farming land as the three grazier-explorers hoped? Or a tremendous river - like the Amazon - that ploughed through the continent to the west coast? Or would they discover what some convicts believed lay beyond the mountains - China. Blaxland, Lawson and Wentworth's expedition had pressed further west than anyone thought possible - and on 28 May, 1813, they accomplished the impossible. Pushing uphill through thick scrub they suddenly found themselves at the edge of a cliff. Before them was a spectacular vista of plains. They had done it - crossed the "impenetrable" Blue Mountains from east to west. Surprisingly, the three explorers' journal accounts don't suggest euphoria. It's possible they didn't fully understand the significance. The great learning experience from my journey across the Great Divide has been an insight into the explorers' achievement. Dr Siobhan Lavelle, archaeologist and historian, put it succinctly: "History is the way people cope with geography." Looking at the rugged wilderness along Mt York Rd on the western edge of the Blue Mountains, I could not think of a better summation of the 1813 expedition. That night they camped on "the edge of the precipice" as Blaxland described. In the morning they would attempt the perilous descent into the mysterious interior.