at the Cohong's control over prices, advances, and exchange rates and predicted the death of trade with China. In fact, the Cohong helped ensure Chinese production met the traders' needs—some ships had previously been obliged to wait as much as a year to be fully stocked—and by 1769, the area was being expanded to make up for an extreme shortness of apartments. In 1748, there had only been eight factories, but there were seventeen by 1770, a number kept up until the great fire of 1822. It was discovered that, rather than depending on the monsoon winds, ships could arrive or depart at any time of year by rounding the Philippines. This opened the trade for smaller craft who might only need a few weeks to complete a visit, where the large company vessels still needed 4 to 5 months at minimum. Subsequently, the British and Americans typically always had ships anchored off Pazhou, allowing them to keep their supercargos and staff in the Guangzhou factories all year. During the 1780s, the Spanish also began to send several ships from Manila each year rather than the single vessel they had previously used; they began renting a permanent factory in 1788. (In practice, senior supercargos tended to prefer Macao during the summer regardless and to send their junior officers to deal with off-season trade.) In 1793, sent George Macartney to request that ports in northern China be opened to trade but was rejected by the Qianlong Emperor, not due to Macartney's refusal to kowtow in the presence of the Qianlong Emperor, as is commonly believed. A second embassy under Lord Amherst fared no better in 1816–1817. The growth of European (particularly British) tea consumption supplemented the port's heavy trade in silk and porcelain. The balancing trade in goods from Europe was poor so payments had to be settled in large volumes of bullion until the trade in opium rose to take its place. In 1835, the medical missionary Peter Parker opened an ophthalmic hospital in the area. Parker commissioned Lam Qua, a Western-trained Chinese painter who also had workshops in the area, to paint pre-operative portraits of patients who had large tumors or other major deformities. The viceroy Lin Zexu's vigorous suppression of the British opium trade precipitated the First Opium War (1839–1842), during which the factories were burnt to the ground. The 1842 Treaty of Nanking ending that war forced