1826. In 1831 Captain Beaufort informed Captain FitzRoy that he had found a savant for the latter's surveying voyage to South America, Charles Darwin. After completing extensive surveys in South America he returned to Falmouth, Cornwall via New Zealand and Australia in 1836. By the time of Beaufort's retirement in 1855, the Chart Catalogue listed 1,981 charts and 64,000 copies of them had been issued to the Royal Navy. In the 1870s, the Royal Naval Surveying Service supported the Challenger expedition, a scientific exercise that made many discoveries, laying the foundation of oceanography. The cruise was named after the mother vessel, . On her circumnavigation of the globe, 492 deep sea soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature observations were taken. The Challenger crew used a method of observation developed in earlier small-scale expeditions. To measure depth, the crew would lower a line with a weight attached to it until it reached the sea floor. The line was marked in 25 fathom intervals with flags denoting depth. Because of this, the depth measurements from the Challenger were at best accurate to 25 fathoms (150 feet), or about 46 metres. As the first true oceanographic cruise, the Challenger expedition established an entire academic and research discipline. During the late 19th century, the UKHO took part in several international conferences, including the International Meridian Conference to determine a prime meridian for international use and other conferences working towards the establishment of a permanent international commission concerning hydrographic matters. Hydrographers to the Admiralty Board during this period included: Rear-Admiral John Washington, Rear-Admiral George Henry Richards, Captain Sir Frederick J. O. Evans and Rear-Admiral Sir William J. L. Wharton. 20th century During Rear-Admiral A. Mostyn Field's term as Hydrographer to the Admiralty Board, the Hydrographic Office lent instruments to the Nimrod Expedition of the British Antarctic Expedition led by Ernest Shackleton in 1907. Following the in 1912, the Safety of Life at Sea (SOLAS) convention was established, as well as the introduction of ice reporting and forecasting. During World War I, while Rear-Admiral Sir John F. Parry was Hydrographer of the Navy, the Hydrographic Office produced numerous new charts and products to support the Royal Navy. Following the war, the First International Hydrographic Conference was held in London. It led to the establishment in 1921 of the International Hydrographic Organization. In the 1930s, the systematic and regular collection