and Arkwright in 1784. Dale later established four mills at Lanark; they were structurally similar to Arkwright's Masson Mill and at least two of the mills used technology developed in the Derwent Valley, although the factory system was different from that used in the Derwent Valley. New Lanark was acquired by Robert Owen in 1799 who developed paternalism further than had been done in the Derwent Valley, experimenting with education for young and old and social control. Saltaire – another World Heritage Site – was founded in 1853 and featured worker's housing and facilities, as well as other elements of the factory system developed by Arkwright. In 1774, the British government passed an act outlawing the export of "tools or utensils" used in the cotton and linen industries. As a result, the only way for the new technologies being developed in Britain to spread to other countries was through industrial espionage. Carl Delius worked in England and gave plans for many of Arkwright's inventions to Johann Gottfried Brugelmann; Brugelmann used the information to establish a mill in Ratingen, near Düsseldorf, which began production in 1784. He named the settlement associated with the mill Cromford. The mill was the first Arkwright mill in mainland Europe. The techniques for spinning cotton developed in the Derwent Valley were also spread to America. In 1790, the United States had fewer than 2,000 spindles which were powered by spinning jennys, compared to 2.4 million machine driven spindles in Britain at the same time. The Arkwright mill was introduced to America by migrants from England, many of whom were unskilled. Among them was Samuel Slater who was from the Derwent Valley and an apprentice of Jedediah Strutt. He founded Slater Mill at Pawtucket, Rhode Island. Many of the technologies developed in the Derwent Valley Mills endured and were adopted for other textile industries; until the mid-20th century, carding was still performed with machinery invented by Richard Arkwright. The factory system made it possible to produce cheap textiles and clothing. Preservation Out of the Arkwright Festival held in 1971, The Arkwright Society was formed. The Cromford Mill complex was bought by The Arkwright Society in 1979, saving the buildings associated with the mill from demolition. The charity purchased the site for the purpose of conservation and with the intention of beginning restoration. The mills had been contaminated by industrial processes involving pigments and dyes which were stored