lasted until the 1707 Act of Union, when high salt duties prevented the German merchants from trading with Shetland. Shetland then went into an economic depression, as the local traders were not as skilled in trading salted fish. However, some local merchant-lairds took up where the German merchants had left off, and fitted out their own ships to export fish from Shetland to the Continent. For the independent farmers of Shetland this had negative consequences, as they now had to fish for these merchant-lairds. Smallpox afflicted the islands in the 17th and 18th centuries (as it did all of Europe), but as vaccines became available after 1800, health improved. The islands were very badly hit by the potato famine of 1846 and the government introduced a Relief Plan for the islands under the command of Captain Robert Craigie of the Royal Navy who stayed in Lerwick to oversee the project 1847–1852. During this period Craigie also did much to improve and increase roads in the islands. Population increased to a maximum of 31,670 in 1861. However, British rule came at a price for many ordinary people as well as traders. The Shetlanders' nautical skills were sought by the Royal Navy. Some 3,000 served during the Napoleonic wars from 1800 to 1815 and press gangs were rife. During this period 120 men were taken from Fetlar alone, and only 20 of them returned home. By the late 19th century 90% of all Shetland was owned by just 32 people, and between 1861 and 1881 more than 8,000 Shetlanders emigrated. With the passing of the Crofters' Act in 1886 the Liberal prime minister William Gladstone emancipated crofters from the rule of the landlords. The Act enabled those who had effectively been landowners' serfs to become owner-occupiers of their own small farms. By this time fishermen from Holland, who had traditionally gathered each year off the coast of Shetland to fish for herring, triggered an industry in the islands that boomed from around 1880 until the 1920s when stocks of the fish began to dwindle. The production peaked in 1905 at more than a million barrels, of which 708,000 were exported. The Local Government (Scotland) Act 1889 established a uniform system of county councils in Scotland and realigned the boundaries of many of Scotland's counties: Zetland County Council, which was created in 1890, was established at County Buildings in Lerwick. 20th century During