Throughout a century and a half of dealings at Canton, European traders enjoyed the same degree of liberty: they were all free to pay whatever prices or imposts the Chinese Hong merchants and customs officials chose to demand. The Chinese wanted neither foreign goods nor foreign traders, but if the latter persisted in buying and selling at Canton, they were expected to submit to strict Chinese regulations or get out. There were rules forbidding any foreigner to live in Canton except during the six-month trading season, rules denying foreign women the right to enter the city, rules against possessing firearms and an absolute ban against bringing foreign warships past the Boca Tigris (Tiger’s Mouth), the fortified strait on the Canton River estuary leading to the city. In practice, the rules were a kind of game; few were consistently enforced unless the Western traders raised a howl over Chinese customs duties or bumptiously insisted on dealing directly with the officials of the Celestial Empire instead of its merchants. Then the reins were yanked up tight, and the commercial interlopers had to obey every restriction to the letter. Foreigners at Canton remained in a weak bargaining position until a few European traders, particularly the English, discovered one product that the Chinese passionately desired. It was compact, easy to ship, extremely valuable, and it brought full payment in hard cash upon delivery. It could be brought from British India in prodigious quantities, and because it contained great value in a small package, it could slip through Chinese customs without the disagreeable formality of paying import duties. This was opium—the most convincing Western proof of the validity of the profit motive since the opening of the China trade. The Chinese appetite for opium became almost insatiable, spreading upward to the Emperor’s official family and draining away most of the foreign exchange gained by exporting tea and silk. The alarmed Emperor issued a denunciation of this “vile dirt of foreign countries” in 1796, and followed it with a long series of edicts and laws intended to stop the opium traffic. The East India Co., worried by repeated threats of imperial punishment, relinquished its control of the opium trade and dropped the drug from its official list of imports. Private traders with less to lose immediately took up the slack, and after opium was barred from Canton, simply discharged their cargoes of dope into a fleet of hulks anchored off the entrance of the Canton River estuary. From the hulks it was transshipped to the mainland by hundreds of Chinese junks and sampans. Chinese port officials, well-greased with graft, never raised a squeak of protest.