Tobias Mayer

Tobias Mayer was born on February 17, 1723 in Marbach a small town on the Neckar river a few miles from Stuttgart. His father was a cart-wright and an engineer who made water systems. When Mayer was young he plagued his mother with requests for paper and writing supplies to copy his father's water system plans. Mayer was orphaned when he was 8 and after a time in an orphanage he was taken on by a shoemaker named Gottlieb Kandler, from whom he learned geometry and architecture. Mayer attended the Latin school in Esslingen where he studied mathematics on his own and reached the top class in two years. He published a book on geometry when he was 18. He attempted to become a artillery officer but circumstances prevented him realizing this goal. He became an excellent map maker and in 1746 he joined the Homann Cartographic Bureau in Nuremberg. In 1751 he was appointed professor of mathematics and economy at the Georg August Academy in Gottingen.

Mayer is mostly remembered for his astronomical observations of the moon. In 1748 and 1749 he made a map of the lunar surface and came to the conclusion that there was no atmosphere on the moon. At the time this was a controversial opinion. His lunar tables, published in 1752, were recommended by the British Astronomer Royal, for their utility in determining longitude while at sea. Mayer's widow received a 3000 pound grant from the British government after bringing them to England.

A crater on the moon is named is named after him. He is often confused with his son, Johann Tobias Mayer, who was a physicist.

Mayer died during the French occupation of Gottingen on February 20, 1762.


References:

Forbes, Eric Gray; "The Life and Work of Tobias Mayer (1723-62)"; Quarterly of the Royal Astronomical Society (1969)8:227-251

Wepster, Steven; "Father and Son Mayer"; Retrieved from staff.science.uu.nl

Tobias Mayer Wikipedia Entry

Victor Hensen

Christian Andreas Victor Hensen was born on February 10, 1835 in Schleswig, which is now part of Germany. His father Hans Hensen was the director of a school for the deaf in Schleswig and his mother, Henriette, was the daughter of the court physician. Hensen graduated from the cathedral school in Schleswig in 1845 and the grammar school at Glukstat, in Holstein in 1854. He studied medicine at the universities of Wurzburg, Berlin, and Kiel, passing his final examination in 1858. In 1859 he completed his thesis on epilepsy and urinary secretions. After finishing his doctorate he worked as a prosector at the University of Kiel. He was appointed professor of physiology in 1871 and he remained there until 1911. In 1867 he became a member of the Prussian House of Representatives. From 1878 he was the director of the institute of physiology at Kiel. In addition to his work on physiology, Henesen was also an oceanographer and lead many oceanographic expeditions.

Hensen's work was involved with many fields of science including physiology, oceanography, and chemistry. His physiological work included describing the structures of the inner ear. These studies led to the discovery of the Hensen duct, Hensen cells and Hensen stripe. These structures and cells are part of the cochlea, the snail shell shaped structure in the inner ear that is responsible for sensing sound waves. Hensen was also able to extract glycogen from the liver and there was a priority dispute about this between him and Claude Bernard. Now it is known that Hensen verified Bernard's work.

Hensen is most remembered for his coining of the word plankton to describe the microscopic sea organisms that form the basis of the ocean's food chain. These organisms include drifting animals, plants, archea, algae, and bacteria. The term plankton describes an ecological niche rather than a specific type of organism. Because they depend on sunlight they are found in greater numbers on the surface of bodies of water. They are found in oceans and lakes and are an important food source for fish and whales. Hensen developed methods of collecting and studying plankton that are still used today.

Hensen died on April 5, 1924.


References:

Press and Communication Services, University of Kiel; "Famous Scholars from Kiel: Victor Hensen"; Retrieved from www.uni-kiel.de

Raica, M.; "A Short Story of Victor Hensen and a Cell of the Inner Ear"; Romanian Journal of Morphology and Embryology (2012)53:855-857

Victor Hensen Wikipedia Entry

Wilhelm Ludvig Johannsen

Wilhelm Ludvig Johannsen was born on February 3, 1857 in Copenhagen, Denmark. He was the son of a Danish Army officer, Otto Julius Georg Johannsen, and Anna Margarethe Dorthea Ebbson. He mastered many languages when he was still young and he passed his qualifying exams, but was unable to go to a university because his family lacked the means, so he was apprenticed to a pharmacist in 1872, For the next seven years he worked as a pharmacist in Denmark and Germany. In his spare time he studied chemistry and botany. In 1879 he returned to Denmark to work as a chemistry assistant in the Carlsberg laboratories where he did his own botany studies. In 1892 he became a lecturer and in 1902 he became a professor at the Copenhagen Agricultural College. In 1905 he was appointed professor of plant physiology and in 1917 he was made rector at the University of Copenhagen.

Johannsen's is best known for his genetic research. He found that there was evidence that natural selection worked in a mixed group of self-fertilizing plants but not individual self-fertilizing plants. This means that in a group of plants that produce genetically identical offspring natural selection selects for some of the plants but individual plants that produce genetically identical offspring are not effected by natural selection and the only differences in offspring are due to environmental factors. This evidence seemed contradict Charles Darwin's theory of evolution, because according to Darwin natural selection gradually changes organisms to better fit their environment. With our modern knowledge of the function of DNA in cells this result makes sense, because we know genetic variation is the result of mutation.

In addition to his research Johannesen was a prolific writer. His genetic textbooks were the most influential of their time. He coined the words "gene", "genotype" and "phenotype". Johannsen was awarded several honorary doctorates, but was appointed professor without having an academically earned doctorate. He was elected to the Danish Royal Academy of Science.

He died on November 11, 1927 in Copenhagen.


References:

Hjermitslev, Hans Henrik; "Wilhelm Ludvig Johannsen (1857-1927)"; retrieved from: darwinakive.dk

Stankus, Tony; "Wilhelm Ludvig Johannsen"; in Biographies of Scientists for Sci-Tech Libraries: Adding Faces to Facts; Psychology Press; 1991

Whilhelm Johannsen Wikipedia Entry

Isaac Roberts

Isaac Roberts was born January 27, 1829 in Groesback, near Denbigh, in northeastern Wales. His father, William Roberts, was a farmer. Even though his family moved to Liverpool, England when he was still young, it was not before he learned to speak Welsh. In 1844 he was apprenticed to a builder, working for John Johnson and Sons. As an apprentice he spent his evenings at the school in the Mechanic's Institute in Liverpool. After finishing his apprenticeship he remained with the same firm which he eventually became a partner and then owner. He retired from building in 1888 to devote his time to science. Initially he studied geology but he later switched his attention to astronomy for which he is mostly remembered.

Roberts was a pioneering astrophotographer of nebulae. His picture of what at the time was called the Andromeda nebula (now known as the galaxy Andromeda) was the first to show its spiral nature. At the time it was not known that there were other galaxies besides our own. It was not till 1924 that Edmund Hubble determined that the universe went beyond the Milky Way galaxy. In addition to his photography Roberts developed an instrument that engraved stellar images onto copper plates called a stellar pantograver. For his pioneering work in astrophotography he was awarded a gold medal by the Royal Astronomical Society. In 1890 he became a fellow of the Royal Society. In 1892 he received an honorary doctorate from Trinity College, Dublin.

Roberts died on July 17, 1904.


References:

Jones, Bryn; "Isaac Roberts (1829-1904)"; Retrieved from: jonesbryn.plus.com.

R.S.B; "Isaac Roberts. 1829-1904"; Proceedings of the Royal Society of London (1904-1905)75:356-362

Isaac Roberts Wikiepedia Entry

Alexandre-Emile Beguyer de Chancourtois

Alexandre-Emile Beguyer de Chancourtois was born on January 20, 1820 in Paris, France. At eighteen he began attending the school of mines at the Ecole Polytechnique. After completing his studies he joined a geological expedition to Turkey, Hungary, and Armenia. When he returned to Paris in 1848 he took a teaching position at the Ecole Nationale Superieure des Mines de Paris. He became a professor of geology in 1876. In 1875 he became the inspector of mines for France, a position he maintained until his death. As inspector of mines he introduced many safety measures including those to prevent a methane explosion.

He is best remembered for being the first to organize chemical elements into a system based on chemical similarities. Using the atomic masses obtained by Stanislao Cannizzaro, he developed a table of sixteen units, the atomic mass of oxygen, that wrapped around a cylinder, like the thread of a screw. This system was not widely accepted  by chemists because when it was originally published the printer did not understand the cylindrical system so there was no diagram printed and when it was later published in a geological journal it was ignored by chemists. The idea that chemical elements have periodic properties or chemical similarities as atomic mass increases eventually was developed by Dimitri Mendeleev into the first periodic table which was able to predict properties of yet undiscovered elements. The periodic table used today is based on that of Mendeleev.

He died on November 14, 1886 in Paris.


References:

Fuchs, Edmond; "Obituary Notice on MA-E Beguyer de Chancourtois, Inspector General of Mines"; Retrieved from: http://www.annales.org

Strathern, Paul; Mendeleev's Dream: the Quest for the Elements; Macmillan; 2001

Alexandre-Emile Beguyer de Chancourtois Wikipedia Entry

John Pringle Nichol

John Pringle Nichol was born on January 13, 1804 in Hunly Hill, in Forfarshire, Scotland. He was the eldest son of John Nichol a gentleman farmer and his wife Jane. He attended grammar school in Hunly Hill and went to Kings College in Aberdeen, winning highest honors in mathematics and physics. After graduation he served as headmaster in the grammar school at Dun. He held a number of headmaster positions until in 1836 he was appointed as the regius professor of astronomy at the University of Glasgow, a position he beat out Thomas Carlyle for. The duties of this position took little of his time, the rest of which he devoted to astronomical observation and  public lectures. Nichol's lectures were noted not only for their rhetorical power, but also scientific accuracy. His lectures were an inspiration to the young William Thompson.

Nichol's used his public lectures to popularize the nebular hypothesis, the theory that the solar system originated from a nebula. This is the current theory of how the solar system formed. Nebulae are large clouds of hydrogen gas. Gravity among the hydrogen molecules causes them to clump together. Stars form from the clumps of hydrogen when the gravitational pressure causes the hydrogen to begin nuclear fusion creating helium. This process takes over a hundred million years in the case of a sun sized star.

Nichol was responsible for the erection of new observatory on Horselethill in the west end of Glasgow and his family lived in a attached house. In addition to his public lectures Nichol was a prolific writer, publishing many popular books of science. His most famous book Views of the Architecture of the Heavens went through seven editions in seven years and won praise from popular writer George Eliot.

He died on September 19, 1858.


References:

Clerke, Mary Agnes; "Nichol, John Pringle"; Dictionary of National Biography, 1885-1900; Vol. 40.

Anon.; "John Pringle Nichol"; Biography from the University of Glasgow.

John Pringle Nichol Wikipedia Entry

Joseph Erlanger

Joseph Erlanger was born on January 5, 1875 in San Francisco, California. His parents, Herman and Sarah Erlanger, were Jewish immigrants to America and he was the sixth of seven children. After only two years of high school he enrolled in the University of California, Berkeley. He was the only one of his siblings to get a college education. He earned his bachelors degree in chemistry from UCB. He then went to the newly organized John Hopkins University medical school, where he received his medical degree in 1899. He remained at Johns Hopkins Hospital until 1906 when he went to the University of Wisconsin. After serving as a professor of physiology at the University of Wisconsin, he took a position as professor of physiology at Washington University in St. Louis, Missouri. He remained there until his retirement in 1946.

Erlanger's field was physiology. His studies included the physiology of the circulatory and nervous systems. His early research was on the human circulatory system. In 1904 he designed a sphygmomanometer, a device for measuring blood pressure. With it he studied relation between blood pressure and orthostatic albuminuria, a condition where protein appears in the urine of standing patients. During the First World War he studied wound shock and he helped develop therapies for it that were used on United States troops in Europe.

Working with his former student Herbert Gasser, Erlanger developed oscilloscope that could record nerve impulses. Up to that point it had been impossible to study nerve impulses directly, as they were too weak to be detected with the available technology. In 1920 H. Sydney Newcomer invented an amplifier that allowed nerve impulses to be detected. Using this amplifier, Erlanger and Gasser developed their oscilloscope. Nerve impulses are electrical currents generated by the movement of sodium ions into the nerve cell. When a nerve cell is stimulated protein channels in the nerve cell's cellular membrane open and sodium ions flood in. The movement of sodium ions into the cell causes a change in the membrane potential and the flood of sodium ions crossing the membrane into the cell moves down the length of the cell, conducted like an electrical current. Using the oscilloscope they developed Erlanger and Gasser found that larger nerve cells conduct impulses faster than smaller nerve cells and that different nerve fibers have different functions. For their pioneering work studying nerve fibers Erlanger and Gasser were awarded the 1944 Nobel Prize in Medicine and Physiology.

Erlanger died of heart failure on December 5, 1955.


References:

Davis, Hallowell; "Joseph Earlanger: 1875-1955"; National Academy Press; 1970

Joseph Erlanger Nobel Biography

Joseph Erlanger Wikipedia Entry