Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is listening for the sound made by vessels. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may be used for robot navigation, SODAR is used for atmospheric investigations; the term sonar is used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from low to high; the study of underwater sound is known as underwater hydroacoustics. The first recorded use of the technique was by Leonardo da Vinci in 1490 who used a tube inserted into the water to detect vessels by ear, it was developed during World War I to counter the growing threat of submarine warfare, with an operational passive sonar system in use by 1918.

Modern active sonar systems use an acoustic transponder to generate a sound wave, reflected back from target objects. Although some animals have used sound for communication and object detection for millions of years, use by humans in the water is recorded by Leonardo da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube. In the late 19th century an underwater bell was used as an ancillary to lighthouses or lightships to provide warning of hazards; the use of sound to "echo-locate" underwater in the same way as bats use sound for aerial navigation seems to have been prompted by the Titanic disaster of 1912. The world's first patent for an underwater echo-ranging device was filed at the British Patent Office by English meteorologist Lewis Fry Richardson a month after the sinking of Titanic, a German physicist Alexander Behm obtained a patent for an echo sounder in 1913; the Canadian engineer Reginald Fessenden, while working for the Submarine Signal Company in Boston, built an experimental system beginning in 1912, a system tested in Boston Harbor, in 1914 from the U.

S. Revenue Cutter Miami on the Grand Banks off Newfoundland. In that test, Fessenden echo ranging; the "Fessenden oscillator", operated at about 500 Hz frequency, was unable to determine the bearing of the iceberg due to the 3-metre wavelength and the small dimension of the transducer's radiating face. The ten Montreal-built British H-class submarines launched in 1915 were equipped with Fessenden oscillators. During World War I the need to detect; the British made early use of underwater listening devices called hydrophones, while the French physicist Paul Langevin, working with a Russian immigrant electrical engineer Constantin Chilowsky, worked on the development of active sound devices for detecting submarines in 1915. Although piezoelectric and magnetostrictive transducers superseded the electrostatic transducers they used, this work influenced future designs. Lightweight sound-sensitive plastic film and fibre optics have been used for hydrophones, while Terfenol-D and PMN have been developed for projectors.

In 1916, under the British Board of Invention and Research, Canadian physicist Robert William Boyle took on the active sound detection project with A. B. Wood, producing a prototype for testing in mid-1917; this work, for the Anti-Submarine Division of the British Naval Staff, was undertaken in utmost secrecy, used quartz piezoelectric crystals to produce the world's first practical underwater active sound detection apparatus. To maintain secrecy, no mention of sound experimentation or quartz was made – the word used to describe the early work was changed to "ASD"ics, the quartz material to "ASD"ivite: "ASD" for "Anti-Submarine Division", hence the British acronym ASDIC. In 1939, in response to a question from the Oxford English Dictionary, the Admiralty made up the story that it stood for "Allied Submarine Detection Investigation Committee", this is still believed, though no committee bearing this name has been found in the Admiralty archives. By 1918, Britain and France had built prototype active systems.

The British tested their ASDIC on HMS Antrim in 1920 and started production in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923. An anti-submarine school HMS Osprey and a training flotilla of four vessels were established on Portland in 1924; the U. S. Sonar QB set arrived in 1931. By the outbreak of World War II, the Royal Navy had five sets for different surface ship classes, others for submarines, incorporated into a complete anti-submarine attack system; the effectiveness of early ASDIC was hampered by the use of the depth charge as an anti-submarine weapon. This required an attacking vessel to pass over a submerged contact before dropping charges over the stern, resulting in a loss of ASDIC contact in the moments leading up to attack; the hunter was firing blind, during which time a submarine commander could take evasive action. This situation was remedied by using several ships cooperating and by the adoption of "ahead-throwing weapons", such as Hedgehogs and Squids, which projected warheads at a target ahead of the

M. Donald Grant

Michael Donald Grant was the chairman and a minority owner of the New York Mets baseball club from its beginnings in 1962 to 1978. Grant was born in Montreal in 1904, the son of Hockey Hall of Fame defenceman Mike Grant, inducted into the Hockey Hall of Fame in 1950; the younger Grant tried his hand at amateur hockey in Canada before coming to the United States in the mid-1920s. Grant moved to New York City in 1924, starting as a hotel night clerk and part-time ice hockey referee, gained a foothold in a career on Wall Street, he worked for Olcott & Co.. E. B. Smith & Co. and, in 1936, Redmond & Co. In 1938 Grant was named a general partner and was, from 1945, a managing director of the brokerage firm Fahnestock & Company. Grant's interest in baseball stemmed from a long-standing friendship with Joan Whitney Payson, who in the 1960s became the Mets' principal owner. Grant was a member of the New York Giants board of directors in the 1950s, he and Payson were the only members of the Giants board who opposed the team's move to San Francisco after the 1957 season.

With the Mets, Grant was known for bringing fan favorite and former Brooklyn Dodgers first baseman Gil Hodges back to New York in 1968 to manage the team. Only one year in 1969, the Mets won their first World Series, beating the Baltimore Orioles, 4 games to 1; the Mets first manager during their first years at the Polo Grounds, former home of the New York Giants was former NY Giants player, Boston Braves and NY Yankees manager, Casey Stengel. After Payson's death, her daughter, Lorinda de Roulet, assumed ownership of the team and delegated a great deal of authority to Grant; however with the success of the 1969 Mets, Grant's baseball knowledge was questioned by lifelong baseball professionals. Whitey Herzog, Director of Player Development for the Mets when they won the 1969 World Series, said that Grant "didn't know beans about baseball."Grant opposed Major League Baseball's move to player free agency, a stance that affected the Mets as its cross-town rival, the New York Yankees, aggressively pursued free agents under majority owner George Steinbrenner.

Grant is notorious for the contentious contract negotiations and subsequent 1977 trade of future Hall of Fame pitcher Tom Seaver from the Mets to the Cincinnati Reds. The controversy was played out on the back pages of New York's tabloid newspapers, with Seaver angrily accusing Grant of planting a negative article mentioning Seaver's wife with New York Daily News sports columnist Dick Young. Seaver's anger at Grant never abated, contending years that Grant possessed "a plantation mentality" toward his players; as further evidence of Grant's failure to foresee the future of baseball and the wealth and popularity of its players, Seaver tells how Grant once confronted him astonished that Seaver would have the audacity to apply for membership in the prestigious Greenwich Country Club in Connecticut. The Mets finished in last place two years in a row in 1977 and 1978. At one point, due to the Mets' futility on the field and low attendance records, Shea Stadium was dubbed by fans as "Grant's Tomb."

Grant was fired at the end of the 1978 season. After his retirement from Wall Street in 1988, Grant managed the Hobe Sound Company real estate investment firm in his new home of Hobe Sound, Florida. Grant wed Alice Waters in 1932. Grant died in Hobe Sound on November 28, 1998, he was survived by his wife, two sons, a daughter, nine grandchildren

Swimming at the 1998 World Aquatics Championships – Men's 100 metre butterfly

The finals and the qualifying heats of the men's 100 metre butterfly event at the 1998 World Aquatics Championships were held on Friday 1998-01-16 in Perth, Australia. Note: This is not a complete list of results; the SwimNews source below lists 70 swimmers entered in the event. One of the non-list swimmers is likely Kamal Salman Masud who set a Pakistan Record of 58.19. 1996 Men's Olympic Games 100m Butterfly 1997 Men's World SC Championships 100m Butterfly 1997 Men's European LC Championships 100m Butterfly 2000 Men's Olympic Games 100m Butterfly "8th FINA World Swimming Championships". "1998 FINA World Championships". USA Swimming