Charles Darwin's Zoology of the Voyage of the Beagle appears.

Martin Barry expressed the belief that the spermatozoon enters the egg.

Alexandre-Edmond Becquerel shows that light can initiate chemical reactions that produce an electric current.

First American patent issued in photography to Alexander Wolcott for his camera.

The first postage stamp, called the "Penny Black" and bearing the image of Queen Victoria, is issued in England.

The oil-immersion microscope is invented by Giovanni Battista Amici (1786-1863), a former professor of mathematics who is now the director of the observatory at the Royal Museum in Florence, and an astronomer to the Grand Duke of Tuscany. The objective lens of this microscope is immersed in a drop of oil which sits on top of the object under study; this helps to minimize aberrations caused by the light source.

Roderick Murchison names the Permian System.

William Smith's nephew John Phillips formally proposes the geologic eras Paleozoic, Mesozoic and Cainozoic (Cenozoic).

Charles Thomas Jackson (1805-1880) discovers the anesthetic properties of ether.

William Henry Talbot patents the Calotype process, the first negative-positive process making possible the first multiple copies.

Henry Fox Talbot introduces his patented calotype (or "talbotype") paper negative process, an improved version of his earlier process that greatly reduces the required exposure time.

In Paris, street lights made from arc lamps are demonstrated.

Charles Darwin's book The Structure and Distribution of Coral Reefs being the first part of the geology of the voyage of the Beagle, is published. During the year Darwin composes an abstract of his theory of species evolution.

Carl Wilhelm von Nägeli (1817-1891) publishes Zur Entwicklungsgeschichte des Pollens. His paper describes cell division in plants with remarkable accuracy, and discusses seed formation in flowering plants.

Richard Owen names Cetiosaurus, the sixth named dinosaur species.

Die Thierchemie, by chemist Baron Justus von Liebig (1803-1873), is published, and the science of biochemistry begins.

The term DINOSAUR is coined by Richard Owen (1804-1892) to describe a class of animals that we now believe were dominant on the Earth for approximately 175 million years.

Based on Agassiz's Ice Age theory, self-taught science enthusiast Charles MacLaren publishes a newspaper article explaining that substantial ice sheets in the northern hemisphere would have lowered global sea level.

German physician and physicist Julius Robert Mayer is the first to state the law of conservation of energy, noting specifically that heat and mechanical energy are two aspects of the same thing.

On the uniform motion of heat in homogeneous solid bodies, by William Thomson, aka Lord Kelvin (1824-1907), is published. Thomson's concern with the physics of cooling bodies will draw him into debates concerning the age of the Earth. In 1846 he calculates that the Earth can be no more than 100 million years old.

The change in the observed frequency of waves emitted from a source, moving relative to the observer, is described by Christian Johann Doppler (1803-1853). This phenomenon is now known as the Doppler Effect.

Louis Agassiz completes Les Poissons Fossiles describing fossil fish of the world. This single monograph increases tenfold the formally described vertebrates known to science.

That the nervous system uses electricity in communicating between different parts of the body is demonstrated by Emil Heinrich du Bois-Reymond (1818-1896). He founds the field of electrophysiology.

John Stuart Mill publishes Logic.

James Prescott Joule determines the mechanical equivalent of heat by measuring the rise in temperature produced in water by stirring it.

Jerome Increase Case, a 24 year-old farmer from Oswego County, New York, introduces the J. I. Case Threshing Machine. The J. I. Case Company will manufacture farm equipment and will become the largest thresher producer in the world.

The first tunnel under the Thames opens on March 25, built by Isambard Kingdom Brunel (1806-1859). {a]The Thames Tunnel{/a} connects Rotherhithe and Wapping, London. Although it was a triumph of civil engineering, the Thames Tunnel was not a financial success. It had cost a fortune to build — £454,000 to dig and another £180,000 to fit out — far exceeding its initial cost estimates. Proposals to extend the entrance to accommodate wheeled vehicles failed owing to cost, and it was only used by pedestrians. It became a major tourist attraction, attracting about two million people a year, each paying a penny to pass through.

Charles Darwin first outlines his thoughts on natural selection in an unpublished essay.

Robert Chambers, a Scottish journalist, publishes (anonymously) his Vestiges of the Natural History of Creation, an early book outlining an evolutionary view of the natural world.

The second part of the Geology of the Beagle, Charles Darwin's Geological Observations on Volcanic Islands Visited During the Voyage of H.M.S. Beagle, is published. Darwin's book claims to supply evidence for the geological theories of Charles Lyell (1797-1875), from areas that Lyell himself had never seen.

That all the cells in an organism are generated from successive divisions of the egg cell is described by Rudolf Albert von Kölliker (1817-1905). Kölliker shows that the egg is itself a cell.

In Hartford, Connecticut, dentist Horace Wells (1815-1848) uses nitrous oxide as an anesthetic; he is the first to do so.

The School of Medicine in Paris creates a gallery of comparative anatomy.

Michael Faraday relates magnetism to light after finding the magnetic field effects the polarization of light in crystals. He proposes that light may be waves of electromagnetism. He also describes the phenomena of diamagnetism and paramagnetism, which he explains in terms of his concept of a magnetic field.

Francis Ronalds invents the first successful camera for continuous recording (the first "movie camera") of the variations in meteorological and geomagnetic parameters over time. A copy of Ronalds' paper describing describing his device maybe obtained HERE.

The bridge spanning the Allegheny River, at Pittsburgh, designed by engineer John Augustus Roebling (1806-1869), opens in May. It is the first wire cable suspension aqueduct bridge in the world.

Karl Wilhelm Von Nägeli shows that plant cells are not formed as buds from the surfaces of existing cells, as was proposed by Theodore Schwann.

Joseph Leidy identifies in pork the parasite that causes trichinosis, a potentially fatal human disease.

James Prescott Joule discovers that the length of an iron bar changes slightly when the bar is magnetized.

Nitroglycerine is discovered by chemist Ascanio Sobrero (1811-1870), although he uses to term "pyroglycerine". Because of the risks involved in its production, it will not be manufactured commercially for more than a decade.

The lock-stitch sewing machine is patented by Elias Howe (1819-1867).

Jakob Mathias Schleiden and Theodor Schwann announce that cells are the basic units of all living structures.

In his Account of a New Anesthetic Agent, obstetrician Sir James Simpson (1811-1870) argues that chloroform, a substance he discovered, is a better anesthetic than nitrous oxide or ether. Simpson has begun to use chloroform as an anesthetic in childbirth.

Über die Erhaltung der Kraft ("On the Conservation of Force"), by Hermann Ludwig von Helmholtz (1821-1894), is published. It articulates what later becomes known as the Conservation of Energy.

The rotary, or "lightning" printing press is patented by Richard March Hoe (1812-1886). It is used first by the Philadelphia Public Ledger.

On the archetype and homologies of the vertebrate skeleton, by Richard Owen (1804-1892), is published. In the book Owen argues that the skull, and other parts of the body, are formed by the modification of the vertebra of different animals.

Richard Owen describes "homologies" — similarities of design in bird wings, fish fins and human hands.

A Neanderthal skull is excavated from Forbes Quarry on the northern side of the Rock of Gibraltar. Over the next few decades, the skull will be stashed in a library cabinet in Gibraltar, dusted off and sent to London, accurately likened to the ancient skullcap from Neander Valley in Germany, nearly named Homo calpicus, and finally stored and largely forgotten in the Royal College of Surgeons.

The American Medical Association is founded in Philadelphia, with a mission "to promote the science and art of medicine and the betterment of public health."

An absolute scale of temperatures is proposed by William Thomson (1824-1907). Thomson will become Baron Kelvin of Largs, in 1892, and the scale will come to bear his name.

Armand Hippolyte Louis Fizeau suggests that light from a source of moving away from the observer will be shifted toward the red end of the spectrum, a phenomenon known as redshift. This is closely related to, but not exactly the same as, the Doppler effect.

Edmond Becquerel makes the first full-color photographs, but they are only laboratory curiosities: an exposure lasting hours or days is required and the colors are so light-sensitive that they sometimes fade right before the viewer's eyes while being examined.

The American Association for the Advancement of Science is founded. Joseph Henry (1797-1898), who had been appointed the first secretary of the Smithsonian in 1846, is the first secretary of the AAAS, which is modeled after The British Association for the Advancement of Science. The British Association has been in existence for 17 years.

The American Association for the Advancement of Science is established.

Botanist Carl Friedrich von Gärtner (1772-1850) publishes Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreiche. The book describes thousands of experiments, many involving the production of hybrids, on more than 500 species of plants. Mendel will study this book in detail when he attends the University of Vienna in the early 1850s, and will cite the book in the opening of his paper of 1865.

Based on a humerus 58 inches in circumference, Mantell names a new dinosaur species: Pelorosaurus, the first recognized sauropod.

Armand Hippolyte Louis Fizeau measures the velocity of light in error by measuring the time it takes for a beam of light to pass between the teeth of a rotating gear. The light is reflected by a mirror and stopped by the next tooth of the gear. The result, 315,000 km/se4c (196,000 miles/sec), is within 5% of today's accepted value.

In describing Sadi Carnot's theory of heat, published in 1824, William Thomson (1824-1907) uses the term THERMODYNAMICS.

The speed of light is measured by physicist Armand Hippolyte Louis Fizeau (1819-1896) to be approximately 186,000 miles per second.

A unmanned Montgolfier balloon is used to drop bombs on Venice. This is the first time a bombing has been conducted from the air.