a more even thickness, using two sets of rollers that travel at different speeds. This principle later becomes the basis of Richard Arkwright's water frame. 1741: John Wyatt, mechanic and inventor, designs and constructs a cart-weighing machine, later referred to as a compound lever weighing machine; the design works by way of levers that hold in place a platform, no matter where the weight is placed the load is transferred to a central lever. Weights attached to that lever then help in obtaining a reading of accurate weight. The simplicity, efficiency and accuracy of the weighing machine prove extremely popular across England, subsequently weighing errors are reduced to approximately one pound per ton, this remains a high standard of measurement into the mid-19th century. 1741: The Upper Priory Cotton Mill opens as the world's first mechanised cotton-spinning factory. It is financed by local businessman Thomas Warren, and opened by John Wyatt and Lewis Paul. 1742: John Baskerville takes out a patent for making metal mouldings, rolling, grinding and japanning metal plates by use of weights, rollers and pickling, which Baskerville uses over the more traditional method of employing screws. This is the first patent for making metal mouldings by passing them through rolls of a certain profile. 1743: A factory opens in Northampton, fifty spindles turned on five of Paul and Wyatt's machines proving more successful than their first mill. This operates until 1764. 1746: The Colmore family release land on what is later to be known as the Jewellery Quarter to help satisfy the demands of an increasing population. 1746: A sulphuric acid factory is set up at Steelhouse Lane to use the lead chamber process invented by its co-founder John Roebuck. Roebuck and local businessman Samuel Garbett later relocate to Prestonpans in Scotland, taking with them several skilled men from the Birmingham factory. It is here in 1762 where Roebuck takes out a patent for making malleable iron. 1748: Lewis Paul invents the hand driven carding machine. A coat of wire slips are placed around a card, which is then wrapped around a cylinder. Lewis's invention is later developed and improved by Richard Arkwright and Samuel Crompton, although this comes about under great suspicion after a fire at Daniel Bourn's factory in Leominster that specifically uses Paul and Wyatt's spindles. Bourn produces a similar patent in the same year. 1757: Rev John Dyer of Northampton recognises the importance