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The second problem was that the tube had to be 58 feet long in order to accommodate the f/10 optical system. Lord Rosse's first efforts in amateur telescope making had produced instruments which were mounted along the lines of Herschel's design – monstrous scaffolding supported by a rotating platform. This gantry arrangement would not do for such a long and heavy tube. Bearings capable of supporting such tremendous weights were not available. The problem was solved with a type of mounting which had not been used before (and has not been used since). Two parallel 70-foot high masonry walls were erected in a North-South direction, and the tube was slung between them. On the bottom of the mirror cell was a large steel ball which fit into a socket set into the ground midway between the walls. The top of the tube was maneuvered by cables and wooden supports strung from one wall to the other. The cables, struts, spars, and supports were constructed so that equatorial tracking motion was possible. The space between the two walls was adequate for tracking objects for one hour before and one hour after meridian passage.