The late 19th century (1851-1894).
Two figures dominate late-nineteenth-century science-Charles Darwin and Louis Pasteur. One explained how life on Earth had evolved, while the other changed humanity's future with discoveries that led to the ability to control diseases. While other scientists had speculated on the possibility that contemporary life forms had evolved from earlier ones, Darwin was the first to lay out in detail the theory of evolution by natural selection. The book that brought his work to the world's attention, The Origin of Species (1859), was the most important scientific work since Newton's Principia. Although at the time there was no fossil data to provide details on the evolution of the human species, in 1871 Darwin published The Descent of Man, an application of his theories to the human race. In 1856 Louis Pasteur discovered that gentle heating kept wine from going sour and prevented the contamination of milk, and in the process he became interested in microorganisms. In 1860 he showed the role they played in the decay of meat. His great contribution came in 1862 when he published evidence for the germ theory of disease. This was the beginning of modern medicine, for now specific and effective steps could be taken toward preventions and cures of diseases. Perhaps the greatest contribution to chemistry during this period was made by Dmitry Ivanovich Mendeleyev, who in 1869 created a table of the elements arranged in order of increasing atomic weight. Electricity also featured strongly in late-nineteenth-century technological innovations. Chief among those who put electricity to work for the masses was Thomas Alva Edison. In 1879, two years after devising the phonograph and after thousands of failed attempts, he passed a current through a filament in a glass bulb and allowed humanity to push back the dark. A decade later and shortly after George Eastman had developed the Kodak Camera, Edison took a series of closely spaced photographs along a strip of film. When the developed film was moved in front of a light, the illusion of movement was created-and the motion picture was born. A year before Edison invented the phonograph, Alexander Graham Bell was searching for a way to transmit not just telegraph signals but the spoken word. He found it in a mechanism that turned sound waves into fluctuating electric current that was reconverted into sound at the other end. Edison helped refine the telephone by increasing the amount of sound the microphone in the mouthpiece could carry. After earlier and less efficient engines by Jean Lenoir and Nikolaus August Otto, Carl Friedrich Benz built the first working automobile with a gasoline-burning internal-combustion engine in 1885. In 1853 George Cayley founded the science of aerodynamics when, in building a glider, he created a successful design by which a heavier-than-air object could be kept aloft. Although no engine of that time could propel such a vehicle, the shape he designed is the one that finally gave wings to human beings.