the width of the bays increased. Specialised mill architects appeared. Mills of this period were tall, narrow, and wide. They were commonly built with one or two wings to form an 'L' or 'U' shape. Brunswick Mill was a 28-bay mill, 6 storeys of 16 m by 92 m. Each self-acting spinning mule had 500 spindles. Single-storey north light weaving sheds were sometimes added to the mills. The looms caused vibrations that damaged the structure of multi-storey buildings, and specialised weaving mills became common. They were single-storey sheds with an engine house and offices, and preparation and warehousing in a two-storey ancillary building. Large mills remained the exception during this period. In 1833 the largest mill was that of McConnel and Company in Ancoats, Manchester with 1,545 workers, but in 1841 there were still only 25 mills in Lancashire with 1,000 workers or more, and the number of workers in the average mill was 193. The Lancashire boiler was patented in 1844, and the economiser in 1845. This can be seen as a square brick structure between the boiler house and the chimney. The engines were double compound upright beam engines of the type patented by McNaught in 1845. Each room in the mill would have line shafts suitable for the type of frame, connected by belt drives or gearing. In 1860, there were 2650 cotton mills in the Lancashire region, employing 440,000 people. The workers, 90 per cent of whom were adults and 56 per cent females, were paid a total of £11.5 million per annum. The mills used 300,000 hp of power, of which 18,500 was generated by waterpower. The mills had 30,387,467 spindles and 350,000 power looms. The industry imported 1,390,938,752 lb of raw cotton a year. It exported 2,776,218,427 yards of cotton cloth and of twist and yarn. The total value of its exports was £32,012,380. 1860 saw the end of this period of rapid growth. The Cotton Famine of 1861–1865 was a period when American long staple cotton became unavailable due to an American Civil War. After the war, the economics of the industry had changed, and a new larger mill was required. United States In 1814 the Boston Manufacturing Company of New England established a "fully integrated" mill on the Charles River at Waltham, Massachusetts. Despite the ban on exporting technology from the UK, one of its proprietors, Francis Cabot Lowell, had travelled to