designed to use the main part of the system, and they generally made the transit from the harbour at Bude, or from Helebridge if trans-shipping from coastal vessels there. After Helebridge, there were three inclined planes to the summit section; the whole of the central part of the system was at this level, above sea level. The main line to Druxton Wharf, near Launceston, negotiated three descending inclined planes as it followed the southerly course of the River Tamar. With no intermediate locks on the tub boat sections, the canal had to follow the contours between the inclined planes, and this made its route even more circuitous than most canals. However, some relatively ambitious viaducts and earthworks were constructed, particularly where side streams and small valleys entered the main watercourse and its valley. The inclined planes The unusual feature of the canal was the six inclined planes. The tub boats had wheels, and on the inclined planes they were pulled up the slopes with the wheels running in channel rails (like a squat letter "U" in section). There were two sets of rails, one for each direction, but it does not appear that a counterbalancing system was used (in which a boat coming down would balance one being pulled up). The tub boats were hauled up and let down the inclined planes by chains, which were operated in most cases by waterwheels; the transit took five minutes or so. There were standby steam engines at some of the inclined planes. However the Hobbacott Inclined Plane (both the steepest and that allowing the greatest height difference) used a different system of harnessing water power: water filled a very large bucket, and it was simply the weight of the water that pulled the ascending tub boat up the incline. The bucket operated in a deep vertical shaft, and at the bottom a plug was opened and the water ran to waste along an adit which connected to the lower level of the canal; the descending bucket pulled an empty bucket up in the same operation. The full bucket had to be heavy enough to pull a loaded tub boat up the 1 in 4 gradient as well as overcoming friction, and Green calculated that a weight of about fifteen tons was necessary. This was successful, and the bucket raised a boat up the plane in about four minutes, which was about one