Alexander Becher is believed to be the first (from 1808–1852) to study travel of so-called "bottle papers" around an ocean gyre (a large circulating current system). In the late 1800s, Albert I, Prince of Monaco determined that the Gulf Stream branched into the North Atlantic Drift and the Azores Current. In the 1890s, Scottish scientist T. Wemyss Fulton released floating bottles and wooden slips to chart North Sea surface currents for the first time. Releasing bottles designed to remain a short distance above the sea bed, British marine biologist George Parker Bidder III first proved in the early twentieth century that deep sea currents flowed from east to west in the North Sea and that bottom feeders prefer to move against the current. The U.S. Coast and Geodetic Survey (C&GS) used drift bottles from 1846 to 1966. More recently, technologies involving satellite tags, fixed current profilers and satellite communication have permitted more efficient analysis of ocean currents: at any given time, thousands of modern "drifters" transmit current position, temperature, velocity, etc., to satellites, thus avoiding conventional drift bottles' dependence on serendipitous finds and cooperation by conscientious citizens. Drift bottle studies have provided a simple way to learn about non-tidal movement of waters containing eggs and larvae of commercially important fishes, for sharing among fisheries scientists and oceanographers. Such experiments simulate the travel of pollutants such as oil spills, study formation of ocean gyre "garbage patches", and suggest travel paths of invasive species. Persistent currents are detected to allow ships to ride favorable currents and avoid opposing currents. Projected travel paths of navigation hazards, such as naval mines, advise safer shipping routes. Even in inland waterways, drifters wirelessly deliver real-time data on water quality, GPS location, and water velocity, for early warning against flash floods, measuring pollution run-off, and monitoring algal blooms. Outside science, people have launched bottled messages to find pen pals, "bottle preachers" have sent "sermon bottles", propaganda-bearing bottles have been directed at foreign shores, and survivors have sent poetic loving tributes to departed loved ones or sent their cremated remains (ashes) on a final journey. It was estimated in 2009 that since the mid-1900s, six million bottled messages had been released, including 500,000 from oceanographers. Bottle design and recovery rates Some bottles are ballasted with dry sand so that they float vertically at or near the ocean surface, and are less influenced by winds and breaking waves than