While numerous crucial improvements were added over the first half of the nineteenth century, the first functioning suspension bridge large enough to transport humans and horses was the Jacob's Creek Bridge, built in the early 1800s by the American judge and amateur engineer James Finley.

STEAM LOCOMOTIVE (1805).

A number of engineers built working steam-powered vehicles, some designed to run on roads, some on rails, in the last decades of the eighteenth century, though historians generally consider the train designed by Richard Trevithick in Wales in 1805 to be the first fully functioning steam locomotive.

PUNCH CARDS (1805).

The idea of using punch cards for programming mechanical looms is generally credited to Joseph Marie Jacquard, but weavers in the early 1700s, including Basile Bouchon and Jean Falcon, experimented extensively with punch card control of warp threads.

SPECTROSCOPE (1814).

German lenscrafter Joseph von Fraunhofer invented the spectroscope, a device that measures properties of light, in order to study dark lines occurring in various forms of spectra, which he later discovered were areas of the spectrum where light is absorbed.

STETHOSCOPE (1816).

A French physician named Rene Laennec invented the stethoscope after improvising one with a roll of paper while treating a woman suffering from heart disease.

BICYCLE (1817--1863).

The first two-wheeled, steerable vehicle was designed by a German baron named Karl von Drais, and mimicked by dozens of entrepreneurs throughout Europe in the following decade. But it wasn't until the 1860s that pedals and rotary cranks were added to the device.

BRAILLE (1821).

Louis Braille, a blind, French fifteen-year-old, invented Braille-a tactile form of reading-by improving upon a more rudimentary system of raised b.u.mp, tactile text (night-writing) conceived by an army captain, Charles Barbier.

ELECTRIC MOTOR (1821--1850).

More than a dozen scientists and entrepreneurs contributed to the design of the electric motor in the first half of the eighteenth century, beginning with the English chemist and physicist Michael Faraday's demonstration, in 1821, of a system for converting electrical energy into mechanical energy.

SECOND LAW OF THERMODYNAMICS (1824).

The second law of thermodynamics, which evolved over the years in the hands of various scientists, including Sadi Carnot and Rudolf Clausius, states a theory of universal entropy that invalidates the possibility of perpetual motion machines.

GEOLOGICAL UNIFORMITARIANISM (1830).

The idea that the geological state of the earth was based on consistent forces acting over very long time scales is largely attributed to Charles Lyell's Principles of Geology Principles of Geology, published in 1830, though the term itself comes from a review of Lyell's book written by William Whewell. Lyell's ideas would subsequently form the platform on which Darwin based his biological theory of evolution.

CHLOROFORM (1831).

Chloroform, a colorless, organic compound, was discovered at about the same time by three different scientists in three different countries-Eugene Soubeiran, Samuel Guthrie, and Justus von Liebig. It was used as a treatment for asthma and as a powerful alternative to ether as an anesthetic.

REFRIGERATOR (1834).

After acquiring a patent for a vapor-compression refrigeration system, mechanical engineer Jacob Perkins invented the first practical refrigerator in 1834, though an earlier refrigeration machine had been invented by American inventor Oliver Evans in 1805.

REVOLVER (1836).

Improving upon the flintlock firing mechanism, in 1836 American inventor Samuel Colt designed and patented the revolver, a handgun that featured a rotating cylinder with multiple chambers for bullets.

PROGRAMMABLE COMPUTER (1837).

Although a working version was never built, Charles Babbage outlined the basic principles of the programmable computer-including the notions of what we now call software, CPU, and memory-in his legendary a.n.a.lytical Engine, which he first published a description of in 1837. Lord Byron's daughter Ada Lovelace wrote the first computer algorithm for the device.

TELEGRAPH (1838).

In an effort to improve clumsier, five-wire models of the telegraph, inventor Samuel Morse and his a.s.sistant Alfred Vail created a one-wire model that used electric signals to shift an electromagnet in a patterned print across paper, known as Morse code.

PHOTOGRAPHY (1839).

Most historians credit French chemist Louis Daguerre with developing the first practical photographic process, which involved fixing images on copper places covered in a chemical substance by exposing them to light. Daguerre's's methods were deeply influenced by the innovations of Frenchman Joseph Niceph.o.r.e Niepce.

VULCANIZED RUBBER (1839).

After years of trial and error, Charles Goodyear discovered vulcanized rubber-which unlike natural rubber, maintained its shape despite exposure to pressure and heat-almost by accident, and fought for the rest of his life to claim royalties on the product. Not long after Goodyear's discovery, Thomas Hanc.o.c.k beat him to the patent.

SEWING MACHINE (1845).

The invention of the modern, practical sewing machine was largely due to the individual innovations of two men, American mechanic Elias Howe, who developed the machine's lockst.i.tch mechanism, and American inventor Isaac Singer, who pioneered the vertical motion mechanism for the needle. The two men would clash over credit for the invention.

NITROGLYCERINE (1846).

Working as an a.s.sistant to professor J. T. Pelouze, Ascanio Sobrero first discovered and synthesized nitroglycerine-aware of its explosive potential, Sobrero warned against incautious use of the chemical and at times even seemed to regret its discovery.

ABSOLUTE ZERO (1848).

Drawing on the work of earlier scientists studying temperature, Kelvin developed absolute zero, which forms the lowest point of his Kelvin scale, representing the point at which all matter ceases to move-roughly 273.15 C.

PIG IRON/STEELMAKING (1850--1860).

Though the process of making steel would continue to be improved for years after Henry Bessemer's innovations, the American inventor discovered the first means to ma.s.s-producing steel. By oxidizing pig iron, Bessemer was able to manufacture comparably high-quality steel in large quant.i.ties, eventually aiding the construction of skysc.r.a.pers.

ELEVATOR (1853).

While rudimentary versions of "lifts" had existed since the Middle Ages, American inventor Elisha Otis sparked wide public use of such machines in 1853 by developing a safety brake, following the introduction of steam and hydraulic elevators around 1850.

ASPIRIN (1897).

While the pain-relieving properties of willow bark, whose medicinal quality derived from the tree's salicin, had been understood and prescribed since Hippocrates, the drug's use had been plagued by side effects, primarily stomach pains. French chemist Charles Gerhardt discovered that adding sodium and acetyl chloride a.s.suaged the intestinal irritation, making for a better drug.

BUNSEN BURNER (1856).

German chemist Robert Bunsen developed the burner in order to carry out experiments on spectral emissions of elements, for which the technology did not yet exist. Stymied by the weak gas burners of the day, Bunsen produced a burner with an incredibly hot and nearly invisible flame, and it became the standard laboratory burner many still use today.

MASON JAR (1858).

Improving upon the inefficient jars commonly used at the time, tinsmith John L. Mason invented a type of jar that would one day bear his name: a blocky gla.s.s container with a screw top and rubber lining to create an airtight seal. The Mason jar became essential in preserving perishable goods.

LEAD-ACID BATTERY (1859).

French physicist Gaston Plante invented the first rechargeable battery while experimenting with the conductive power of rolled sheets of lead and sulfuric acid.

NATURAL SELECTION (1859).

Natural selection was first formulated by Charles Darwin in the late 1830s, though he did not publish his ideas until 1859 in his book The Origin of Species The Origin of Species, after being spurred on by the very similar theories that had been independently developed by the British naturalist Alfred Russel Wallace.

GATLING GUN (1861).

Laboring under the belief that a revolving machine gun would create less bloodshed on battlefields by reducing the number of soldiers needed, inventor Richard Gatling created the Gatling gun, a hand-cranked continuously and rapidly firing weapon drawn on two wheels.

VACUUM CLEANER (1861).

Though many inventors created versions of what we know today as a vacuum cleaner in the late nineteenth century and early twentieth century, Ives W. McGaffey patented the first manually powered vacuum cleaner-or "sweeping machine"-in 1861, marketing the device's ability to clean carpets.

PLASTIC (1862).

British metallurgist Alexander Parkes developed the first major commercial man-made plastic-a synthetic material made from cellulose and treated with nitric acid-and debuted it at the 1862 World's Fair in London. Improvements were made on the material through the nineteenth and twentieth centuries.

GERM THEORY (1862).

While the idea that germs carried contagious disease was not new and had been proposed before, French chemist Louis Pasteur was one of the first to develop experiments to prove the theory conclusively.

DYNAMITE (1863).

Seeking to develop new methods for blasting rock more effectively, Swedish industrialist Alfred n.o.bel built on his experiments with nitroglycerin and invented a detonator that used a strong shock to spark explosions, which he patented in 1863.

PERIODIC TABLE (1864).

In 1864, Russian chemist Dmitri Mendeleev developed upon earlier notions of British chemist John Newlands that chemical elements could be arranged in a pattern according to their atomic ma.s.ses, providing a more comprehensive chart with a focus on recurring trends in properties.

DISCOVERY OF BENZENE STRUCTURE (1865).

Following the discovery of benzene in 1825, German chemists Joseph Loschmidt and August Kekule von Stradonitz theorized a similar structure of the organic chemical compound-a ring of six carbon atoms with alternating single and double bonds. Kekule's discovery was inspired by his legendary dream of the tail-swallowing serpent.

HEREDITY (1865).

The idea that parents pa.s.s certain hereditary qualities to their offspring was originated by Augustinian monk and scientist Gregor Mendel from his work on plants, though his principles were synthesized into a wider theory of genetics by Thomas Hunt Morgan in the early twentieth century.

TYPEWRITER (1868).

After the invention of an inefficient typographer machine in 1829, American inventor Christopher Latham Sholes patented the first practical typewriter in 1868 with the help of his a.s.sociates, pioneering a type-bar system and the QWERTY arrangement of keys to avoid jamming.

TELEPHONE (1876).

The patent for the invention of the telephone was a hotly contested item, leading to a last-minute race to the patent office between American engineer Alexander Graham Bell and American electrical engineer Elisha Gray. Bell ultimately received the patent for the device, which transmitted voice signals electrically.

ENZYMES (1878).

First named by German doctor Wilhelm Kuhne in 1878, enzymes-proteins that act as catalysts for chemical reactions by speeding up the process-were more fully understood due to the studies of German chemist Eduard Buchner and French chemist Louis Pasteur.

LIGHTBULB (1879).

By using electricity to heat a filament, causing it to glow and create light, American inventor Thomas Alva Edison is often considered the inventor of the lightbulb, replacing gas lighting as the main source of illumination. But Edison's work built on the designs of at least a half dozen other inventors who went before him, including Joseph Swan and William Sawyer.

CELL DIVISION (1879).

The discovery of cell division, the process known as mitosis among eukaryotes in which a parent cell divides into daughter cells, was the joint discovery of German biologist Walther Flemming, Eduard Strasburger, and Edouard van Beneden.

SEISMOGRAPH (1880).

Hired by the j.a.panese government to study tremors and earthquakes, three British scientists worked on creating a device that could measure and cla.s.sify the strength of earthquakes, now known as a horizontal seismograph, characterized by its use of a pendulum. Of the three, John Milne generally receives the lion's share of credit for the invention.

INFANT INCUBATORS (1881).

Inspired by the use of an incubator for baby birds, French obstetrician etienne Stephane Tarnier began putting infant incubators-heated cribs for newborns-into regular practice in hospitals. The original designs for the infant incubator were created by French surgeon Jean-Louis-Paul Denuce and German gynecologist Carl Crede.

WELDING MACHINE (1885).

Russian inventors Nikolai Bernardos and Stanislav Olszewski created the first electric arc welder in 1885, though the principle underlying welding-that the application of heat can be used to join metallic pieces-had been understood and utilized for centuries.

MOTORCYCLE (1885).

German inventor Gottlieb Daimler expanded upon Nikolaus Otto's internal-combustion engine by connecting it to a bicycle, thus powering the vehicle by gas, not manpower. A steam-engine device resembling a modern motorcycle was invented in 1867.

AUTOMOBILE (1885).

In roughly the same year, 1885, German engineer Gottlieb Daimler and Wilhelm Maybach created a four-wheel, four-stroke engine automobile and German engineer Karl Benz, who most historians credit as the ultimate inventor of the modern automobile, designed a motor car powered by an internal combustion engine and gasoline.

INDUCTION MOTOR (1885).

Both Italian physicist Galileo Ferraris and Austrian inventor Nikola Tesla filed patents in the same year for the induction motor, an alternating current motor that functions via electromagnetic power.

CALCULATOR (1885).

Following centuries of attempts to develop a reliable calculating machine, American inventor William Seward Burroughs created a "calculating machine" in 1885 that formed the basis for all further improvements in calculators.

CONTACT LENSES (1887).

Though Leonardo da Vinci is said to have sketched the first designs for corrective vision lenses, German gla.s.sblower F. A. Muller first conceived of lenses that would replicate the shape of the human eye and improve vision. With the help of his a.s.sistants, German physicist Adolf Eugen Fick further improved the design by creating lenses that conformed to the eye more comfortably than any previous version.

EKG (1887).

The EKG evolved over a string of developments, though the most important contribution may have been Augustus Waller's in 1887; Waller was the first scientist to publish an EKG by attaching an electrometer to a projector.

MOTION PICTURE CAMERA (1888).

American inventor Thomas Edison patented one of the early versions of a motion picture camera-which he called a "kinetoscope"-but his device drew heavily on similar work done by English photographer Eadweard Muybridge and the discoveries of other experimenters with the photographic medium in the late nineteenth century.

MITOCHONDRIA (1890).