depressed state of the economy caused smuggling to become a mainstay of Gibraltar's trade; the mid-19th-century Irish traveller Martin Haverty described Gibraltar as "the grand smuggling depot for Spain". General Sir Robert Gardiner, who served as Governor between 1848 and 1855, described the daily scene in a letter to British Prime Minister Lord Palmerston: The problem was eventually reduced by imposing duties on imported goods, which made them much less attractive to smugglers and raised funds to make much-needed improvements to sanitation. Despite the improvements made earlier in the century, living conditions in Gibraltar were still dire. A Colonel Sayer, who was garrisoned at Gibraltar in the 1860s, described the town as "composed of small and crowded dwellings, ill ventilated, badly drained and crammed with human beings. Upwards of 15,000 persons are confined within a space covering a square mile [2.5 km2]." Although there were sewers, a lack of water made them virtually useless in summer and the poorer inhabitants were sometimes unable to afford enough water even to wash themselves. One doctor commented that "the open street is much more desirable than many of the lodgings of the lower orders of Gibraltar." The establishment of a Board of Sanitary Commissioners in 1865 and work on new drainage, sewerage and water supply systems prevented further major epidemics. A system of underground reservoirs capable of containing 5 million gallons (22.7 million litres) of water was constructed within the Rock of Gibraltar. Other municipal services arrived as well – a gas works in 1857, a telegraph link by 1870 and electricity by 1897. Gibraltar also developed a high-quality school system, with as many as 42 schools by 1860. By the end of the 19th century, the "Gibraltarians" were given an official identity for the first time. It was only in the 1830s that Gibraltar-born residents began to outnumber foreign-born, but by 1891 nearly 75% of the population of 19,011 people were Gibraltar-born. The emergence of the Gibraltarians as a distinct group owed much to the pressure on housing in the territory and the need to control the numbers of the civilian population, as Gibraltar was still first and foremost a military fortress. Two Orders in Council of 1873 and 1885 stipulated that no child of alien parent could be born in Gibraltar, no foreigners could claim a right of residence and that only Gibraltar-born inhabitants were entitled to reside there; everyone else