On the western side coming from Ashton‑under‑Lyne the waterway rises through 334 feet using 32 locks; on the eastern side it descends to Huddersfield by 436 feet using 42 locks. Although boring a tunnel through the Pennines was by far the greatest engineering challenge in constructing the canal, creating these 74 locks on a canal just under 20 miles long was also a major undertaking. In this section there are nine locks known as the Diggle Flight. They were built under the direction of the engineer Thomas Telford and have an unusual – and it is thought unique – design. There are single gates at either end of each lock (head and tail gates) with pairs of inclined paddle gear. Note that the beams do not stick out onto the towpath but onto the opposite side. The locks were worked entirely from that side and this design enabled a more speedy passage by horse-drawn narrowboats. Since water can only flow downwards through locks, every time a lock was used a lockful of water moved away from the highest point. An adequate supply of water was needed to keep the canal operational so a series of reservoirs were built. Brun Clough Reservoir that we saw near Standedge Cutting was one of ten that gathered rainwater from the hillsides of the Pennines to meet the needs of the canal. Unfortunately, despite all the cost and effort, the canal was not very profitable. The nearby Rochdale Canal, which opened in 1804, also offered a routeway across the Pennines linking the Bridgewater Canal in Manchester with the Calder and Hebble Navigation at Sowerby Bridge. This 32 mile long waterway was a ‘broad’ canal rather than a ‘narrow’ canal meaning that its locks were twice the size. So while the Rochdale Canal could process two boats at once, here on the Huddersfield Narrow Canal, boats had to wait their turn in the basins by each lock. Furthermore, Standedge tunnel, constructed without a towpath, proved to be a bottleneck while the Rochdale Canal had no unpleasant, time-consuming summit tunnel. From the 1840s onwards both canals suffered competition from the railways. Traffic on the canal was maintained until the turn of the century but declined sharply during the First World War. The last working boat passed through in 1921 and the canal was officially closed in 1944 after which it soon fell into disrepair. Directions to stop 19 Continue along either side of the canal towpath. Immediately after Lock 24W the canal goes under Bridge 70. If you want refreshments you can leave the towpath here and divert to the Navigation Inn just 100 metres up Wool Road. Otherwise continue under the modern road bridge (Number 71). Immediately afterwards is a warehouse with an overhanging roof on the opposite side of the canal. Stop here.