increased fivefold between 1821 and 1837, and usage of the drug became more widespread across Chinese society. The Qing government attitude towards opium, which was often ambivalent, hardened because of the social problems created by drug use and took serious measures to curtail importation of opium in 1838–39. Tea had become an important source of tax revenue for the British Empire, and the banning of the opium trade and thus the creation of funding issues for tea importers was one of the main causes of the First Opium War. While waging war on China was one of Britain's tactics, it also began to use India for growing tea. After tea plants were smuggled out of China, plantations were established in areas such as Darjeeling, Assam, and Ceylon. As an attempt to circumvent its dependence on Chinese tea, the East India Company sent Scottish botanist Robert Fortune to China to purchase and bring out of China tea plants, which were then taken to India. With the exception of a few plants which survived in established Indian gardens, most of the Chinese tea plants Fortune introduced in the north-western provinces of India perished. Due to the British preference and fashion for a strong dark tea brew, which was discovered to be best made from the native varieties of tea plant in India Assam subspecies (Camellia sinensis var. assamica), it proved more important for the development of production there. However the technology and knowledge that was brought from China was instrumental in the later flourishing of the Indian tea industry in Assam and Sri Lanka. Tea remained very important in Britain's global trade, contributing in part to Britain's global dominance by the end of the 18th century. To this day tea is seen worldwide as a symbol of 'Britishness', but also to some, as a symbol of old British colonialism. The Americas The drinking of tea in the United States was largely influenced by the passage of the Tea Act and its subsequent protest during the American Revolution. Tea consumption sharply decreased in America during and after the Revolution, when many Americans switched from drinking tea to drinking coffee, considering tea drinking to be unpatriotic. The American specialty tea market quadrupled in the years from 1993 to 2008, now being worth $6.8 billion a year. Specialty tea houses and retailers also started to pop up during this period. Canadians were big tea drinkers