Selecting the Line of Road
It is worth noting here some sections from a book by Edward Dobson on Pioneer Engineering (1877), in the chapter on Selection of Road-Lines. It was written well after the Great North Road construction but his references to the difficulties and choice of road-lines encountered in mountain range road construction are interesting. The comments reflect what must have been in Major Mitchell's approach to solving some of the GNR route problems.
The first operation is to find the point of the range to be crossed, taking barometer readings along watersheds to find the altitude of each point of observation. The next step is ascertain the distance from the foot of the pass to the summit on the ridge. This enables the effective gradient to be estimated approximately and thence to determine the most favourable ground to be used.
He draws attention to the situation that it generally happens that opposite sides of a range present very different conditions, a gradual rise on one side and a precipitous gradient on the other. In the latter case, it is necessary to determine the distance required for a practicable gradient by doubling the distance up the rise by forming zig-zags, remembering that the expense of making suitable turning places is very great with the additional length of road required being considerable. All turning places should not only be level but should be sufficient length for a time to halt on before turning. The plan is to select suitable spots for turning-places, and then to connect these binding points by the easiest gradient that the ground will allow. While this might mean some quite severe excavations, it is better than tight corners.
He gives a simple case in the figure where things have been "judiciously treated". In this figure, the turning places at a and b are on easy curves and on nearly level ground. If we take this example back into the past with Major Mitchell looking at how to go about getting up to the north from the Hawkesbury River, it is clear that Mitchell thought along the same lines that Dobson was advocating.
Finch's Ascent v. Devine's Hill
The problems which confronted Heneage Finch and Percy Simpson in establishing a suitable way up the steep inclines on the northern side of the Hawkesbury River have already been mentioned. Construction of the road along the route surveyed by Heneage Finch in 1825 had been under way for some time before there was a visit to the area by Governor Darling and Major Mitchell in October 1828. It seems that they did not approve of the zig-zag route up the eastern slope of Roses Run, with the turns being far too tight for cartage to be undertaken safely. By courtesy of Ian Webb, we reproduce part of his map of Finch's Ascent up from the Hawkesbury River at the original Wiseman's Ferry crossing. The zig-zag line up the hill must have been what upset Governor Darling. The turning points were sharp and difficult for a cart drawn by horses or bullocks. Even each zig or zag had an appreciable gradient as well, perhaps 1 in 3 or 4. Just walking up the old roadway these days is quite a steep climb.
Darling instructed Mitchell to undertake a survey to determine a better line of ascent. Mitchell instructed Finch to investigate other lines of ascent in October 1828 on the western side of the ridge. Finch submitted two alternate lines in December 1828 but it seems that Darling and Mitchell did not approve of either proposal. Darling instructed Mitchell to "attend to the line of ascent himself". This he began on 17 January 1829 and he reported that "after some days of reconnaissance and making a survey, the line of ascent was found" to the east of land owned by Molly Devine, following the eastern side of a gully to the top of the hill and then eastward to link with Finch's line on the ridge. In the construction phase which followed, Mitchell measured the height of junction of the two road lines and recorded it as being 574.5 feet (175 m) above the River. No doubt he had used his barometer in just the same way during his reconnaissance of January 1829 to get the best gradients up Devine's Hill to meet the Finch Ascent road.
A present day RTA map developed for the Convict Trail Project gives a clear picture of the difference between the two routes which join together on the ridge above. From there onwards, the route was north but there were still some quite severe problems to be overcome.
When the decision was made by Mitchell to transfer all work to the Devine's Hill line of road, work stopped completely on the Finch Line. Mitchell had remarked that he anticipated that the Devine's Hill Ascent would be in operation within six months. In January 1830, Simpson reported that "the cart team may be able to go up the new line by Devine's Hill in about three months". Nevertheless, work was still going on on the new line and passage there would have been difficult and probably dangerous too. It seems probable that the Finch Ascent would have been used as that part of the road north until at least 1831 though there would have been incomplete or even unmade road from the top of the Finch Ascent to the new junction point with the Devine's Hill line.
On the map are marked some of the important items in the Convict Trail Project listing of significant sites.
- Convict Stockade Site 1 - Southside of river
- Convict Stockade Site 2 - Northside of river
- Wiseman's Ferry Hotel
- Powder Magazine below Finch's Ascent
- Original Ferry Crossing
- Present Ferry Crossing
- Convict Bridge on road to Devine's Hill Ascent
- 1828 Ascent - Finch's Line
- Devine's Hill Ascent
- Cave near top of Devine's Hill Ascent
- Carving near last loop in Devine's Hill Ascent
- Shepherd's Gully Road
Wiseman's Ferry
You will have gathered that the ferry service operated by Wiseman was in existence at the time of the construction of the road to the north. It was rowed across the Hawkesbury and it is possible at some stage that there was a rope across as well. Drawings or paintings have not been found which give a clue to the original ferry.
Nevertheless, among some archival photographs from around the turn of the 20th century, there is a photograph of the ferry operating at that time, using a rope across the river from the same location as the modern ferry. The photograph has been taken from the north bank when the ferry was getting ready to move back to the south side. The ferryman appears to be getting into action on the rope system. The road up the slope and then to the west is the road which is now the main road along the north side of the river. With so much mention of Wiseman and his Ferry in these pages, we hope you will admire both this ferry and the view up the river at the turn of the 20th century.
References:
Dobson, Edward, Pioneer Engineering, London (1877).
Newell, H.H., Road Engineering and its Development in Australia 1788-1938, Journal of the Institution of Engineers, Vol. 10, parts 2, 3 (1938).
Upton, T.H., The Establishment of Direct Road Communication between Sydney and Newcastle, Journal of the Institution of Engineers, Vol.4, parts 5, 6, 7 (1932).
Webb, Ian, Blood, Sweat and Irons, Dharug & Lower Hawkesbury Hist. Soc., p.32.
Convict Trail, Great North Road, A Set of 41 Maps, prepared by S. Lavelle, Dr G. Karskens and RTA Technology.
