#p <nat>English<o>philosopher<n>William of Occam<sur>Occam<b>1285<d>1349(1)<c>Surrey
#p <nat>German<o>monk<n>Johannes Trithemius<b>1475(15)<d>1525(15)<c>Germany<info>Trithemius of Spannheim was elected abbott of the Benedictine Abbey of Saint Martin at age 22. He was the teacher of two prominent heretics, Cornelius Agrippa and @Paracelsus@@. He is considered to be the father of modern cryptography. In 1510, Trithemius wrote Polygraphia. He introduced for the first time the concept of a square table, or tableau, in which the normal alphabet was successively shifted a predetermined number of spaces.<ref>J. Satinover, pg. 94
#p <nat>Flemish<o>geographer<n>Gerardus Mercator<b>1512 Mar 5<d>1594
#e <t>discovery<p>Mercator<n>earth's magnetic pole<d>1546<info>by @Gerardus Mercator@@
// 18th century
#p <nat>German<o>scientist<o>explorer<n>Alexander von Humboldt<b>1769<d>1859
#p <nat>American<o>meteorologist<n>William Ferrel<b>1817<d>1891<c>Pennsylvania<info>Ferrel explained in 1858 how the earth's rotation affects the way weather moves. The Ferrel cell, of which he conceived, is the middle latitude (30-60 degree) "wheel" of the atmosphere's general circulation as seen in the latitude-height plane. Three such cells exist in the classical view: a "direct" tropic cell and a "direct" polar cell (in which warm air rises and cold air sinks), with a reverse middle latitude cell in between.<ref>Grolier
// 20th century
#e <t>theory<t>geology<d>1912<n>continental drift<c>Germany<info>by Alfred Wegener
#e <t>disc<d>1913<n>ozone layer<c>France<info>Charles Fabry discovered a layer in the atmosphere that shields earth from the sun's ultraviolet rays.
#e <t>disc<d>1924<n>ionosphere<info>Edward Appleton proves the existence of the ionosphere. Such a layer of ionised air had been theorised in 1912 by William Eccles.
#e <t>geology<d>1935<n>Richter scale<c>U.S.<info>developed by American seismologist Charles Richter for measuring the strength of earthquakes.
#e <t>theory<t>geology<d>1938<n>Greenhouse effect<c>Great Britain<info>British engineer George Callendar analyses decades of temperature readings and describes what is later known as the Greenhouse effect.
#e <t>discovery<d>1991<n>Ice man<c>Italy<info>Tourists hiking in the Tyrolean Alps discover a body protruding from a glacier. It turns out to be the freeze-dried remains of a man who died about 3300 B.C.