Secondary School Level

"A garden sprinkler [in one hour] uses the same amount of water as a family of four in one day." Caroline Roux, Journalist During the nineteenth century, the United States saw many people moving out of the city centers into the burgeoning suburbs. With more space, people began to develop an interest in cultivating gardens. The widespread introduction of city water systems also brought water to more homes. There are thousands of sprinkler patents, and it is difficult to credit the invention to one person. American Joseph Oswald's sprinkler was not the first to be patented, and his application described it as making "improvements in lawn sprinklers." His design improved the way in which the head of the sprinkler moved and also dealt with the issues of wear and tear that occurred because of the constant motion of the sprinkler. Earlier sprinklers had often been static, but Oswald's was one more...

"If I had been technically trained, I would have quit, or probably would have never begun." King Gillette, American businessman Before the safety razor was invented, the dangers of shaving were evident in the description of the traditional instrument as a "cut-throat" razor. Shaving was a tricky operation, typically carried out by barbers or trusted family members rather than individuals. To protect the skin while shaving, a Frenchman, Jean-Jacques Perret, introduced one element of the safety razor in the late eighteenth century namely a guard. Inspired by the design of a carpenter's plane, he used a wooden sleeve around the blade so that only the leading edge protruded. However, the first true safety razor, combining both a guard and a removable blade, was introduced in the United States in 1875 by the German Kampfe brothers (Frederick, Richard, and Otto). The Star Razor featured a hoe-type razor with a wedge-shaped blade more...

"The driver of a racing car is a component.... I changed gear so hard that I damaged my hand" Juan Manuel Fangio, Formula One World Champion Changing gear while driving a car is something we take for granted; but in the early days of motoring it was a much more delicate operation that required a lot of skill and practice. With the old straight-cut gears, the rotational speed of the gears had to be the same before they could be meshed together to power the wheels. However good a driver you were , the result was often a terrible grating noise. Drivers had to use a complicated procedure known as double declutching. When changing up a gear the driver had to disengage the clutch, switch to neutral, and let the engine run down to a slower speed. It was necessary to re-engage the clutch for a moment, which slowed down more...

"The faster the drill rotated, the less discomfort the patient experienced." Malvin E. Ring, dentistry historian As long as 5,000 years ago, people were using bow drills to bore into teeth. Later, the Greeks and Romans drilled teeth for rudimentary purposes, but the art was lost in the Dark Ages. Precision drilling was reinvented by French physician Pierre Fauchard in 1728, but many crucial subsequent developments came from the United States. George Washington's dentist, John Greenwood, developed the first powered drill, enabling more accurate and faster drilling through the use of a foot treadle (taken from a spinning wheel). Englishman George Harrington refined this with a motor in 1864, but the most important developments of the era were by an American engineer and inventor, George F. Green from Kalamazoo, Michigan. In 186S Green redesigned Harrington's drill using compressed air. He had worked on several prototypes while employed by the S. more...

Electric turn signals, or indicators, are now a standard feature of virtually all motor vehicles. They are essential for warning fellow road users of intended movements to avoid collisions. Before their invention, drivers had to rely on good old-fashioned hand signals to let others know when they intended to turn. It is thought that the first automatic turn signals were patented in 1907 by an Englishman called Percy Seymour Douglas-Hamilton. His so-called "devices to indicate the intended movement of vehicles" were in the shape of hands to mimic the manual signals in use at the time. Some years later, in 1925, Edgar A. Walz Jr. obtained a patent for a modern turn signal, but car manufacturers at that time were not interested. The first company to incorporate electric turn signals into a commercial car was Buick. They introduced the device in 1938 as a safety feature and advertised it as more...

"1. Find out what the typical housewife really wants.   2. Produce it!” Kenwood dishwasher ad, 1965 The dishwasher was invented in the nineteenth century, not by a busy housewife or a restaurant owner looking to speed up the kitchen dishwashing, but by a well-to-do American socialite who was tired of her servants chipping her plates. The first patent for a dishwasher was granted in 1850 to John Houghton, but his design proved to be impractical. Josephine Cochrane (1839-1913), the daughter of a civil engineer, came up with a machine, patented in 1886, that was not dissimilar to the dishwasher we use today. Plates and cups were supported in a wire rack lying flat in a copper boiler and blasted with pressurized water until clean. The machine created interest among Josephine's friends who began putting in their orders, and, following a showing at the Chicago World's Fair in 1893, Josephine more...

German scientist Carl von Linde (1842-1934) first invented a way to turn gases into liquid. His discovery would form the basis of modern refrigeration and liquid air production. From the 1600s scientists had known that temperature affects whether a substance is in a gaseous or liquid state. By cooling and pressurizing a gas, it is possible to slow the molecules down and compress them until they collapse and form a liquid. French mathematician Gaspard Monge first produced liquid sulfur dioxide in 1784, and by the late 1800s most gases had been successfully liquefied. However, it was still not possible to produce large quantities suitable for commercial use. Von Linde had the bright idea of using air itself as a coolant. In 1894, in response to a request from the Guinness brewery in Dublin, Ireland, to create a new refrigeration system, von Linde succeeded in liquefying air by first compressing it more...

"Well, it was kind of an accident, because plastic is not what I meant to invent." Leo Baekeland, Belgian-American chemist A few lucky individuals change history and, at the same time, make a lot of money. Such was the case with Belgian-born Leo Hendrik Baekeland (1863-1944), who proved to have a keen eye for opportunity and the drive and know-how to see a project to fruition. Baekeland's first major invention was a dramatic improvement in photographic paper. Eastman Kodak purchased his invention (dubbed "Velox") for upwards of three-quarters of a million dollars in-1898. Freed from financial worry, Baekeland then had his days free to experiment in his laboratory. As the electronics industry grew in the late nineteenth and early twentieth centuries, so did the demand for insulators. Greatly in demand at this time was shellac, a natural product made from a beetle indigenous to Asia. It also turned out to more...

Few other names are as synonymous with invention and innovation in the field of munitions and weapons as that of the Maxim family. This remarkably inventive family's output was not exclusively weapon-related. Indeed, Hiram Percy Maxim's (1869-1936) creation—which enabled a firearm to be discharged without the traditional loud bang—initially stemmed from his interest in automobile design, specifically exhaust silencers or "mufflers." The bulk of noise produced by a firearm discharging subsonic ammunition is caused by a massive and rapid expansion of propellant gases leaving the muzzle, a bit like uncorking a bottle of fizzy champagne. Maxim's silencer—which, like all such devices, suppresses rather than truly silences— attaches to the barrel of a firearm. Essentially a cylindrical casing of much larger capacity than the barrel, and containing a series of baffles, it allows the explosive gases from the cartridge to expand and slow prior to hitting the surrounding air, producing far more...

It was at the 1900 Paris Exposition that the first public demonstration of sound and vision in a movie theater took place. However, projecting volume into a large auditorium was difficult at a time when amplified public address systems did not yet exist; furthermore, the crude synchronization of sound and vision was simply a case of starting the movie projector and audio playback cylinder at the same moment and hoping for the best. Low-key experimentation continued over the next two decades until, in 1919, electrical engineer Lee De Forest (1873-1961) developed the first sound-on-film technology: a system where a soundtrack "strip" was added to the movie film. Four years later, on April 23, 1923, De Forest's Phonofilms studio was responsible for the first public screening of a fully synchronized talking picture. A year later he made the first commercial dramatic talking picture, Love's Old Sweet Song, directed by H. Manning more...