Friedrich Heinrich Alexander, Baron von Humboldt, was one of the great naturalists and more prolific writers of the early 19th century. He was born in Berlin in 1769 and travelled widely at various stages in his life.
In between his voyages, he committed his thoughts copiously to paper, on subjects as varied as the igneous origins of rocks, terrestrial magnetism, and the distribution of plants around the world. His travels in South America, for example, resulted in a work of 30 volumes, and his Kosmos, written between 1848 and 1852 and compressed into a mere four books, was a tour de force of the entire scientific spectrum that ensured his eternal reputation.
Humboldt made a number of important contributions to meteorology.
He devised, for example, a way of picturing the distribution of heat over the Earth's surface, by drawing lines, which he called isotherms, joining places having the same average temperature on a map.
He introduced his isotherms to the Academie des Sciences in Paris in 1817, and so enthusiastic was the reception that by 1820 meteorologists all around the world were drawing isolines of every kind - lines of equal barometric pressure, of annual precipitation and the frequency of thunderstorms, as well as of temperature and the deviation of the temperature from normal.
Some of his ideas, however, might strike us now as being a little quaint. He defined climate, for example, as "all changes in the atmosphere affecting the human organs".
Later climatologists, sensing perhaps there was something unsatisfactory, indeed humanly chauvinistic from the point of view of plants and animals about this definition, came to think of climate as more "the average of the weather", a description that is still quite often used.
Moreover, Humboldt was aware of Aristotle's challenging ideas on seismology. "Earthquakes," the latter wrote authoritatively, "are sometimes preceded during the day, or after sundown in clear weather, by a thin layer of cloud that spreads out into space."
And sure enough, when living in Venezuela in 1799, Humboldt himself noticed a "red fog" on the horizon for several successive days; around the same time the stars flickered a great deal more than usual in the night-time sky, and a 12-degree halo formed around the moon. "The inhabitants," he wrote, "are most firmly convinced of a connection between this state of the atmosphere and a trembling of the ground."
Sure enough, these unusual displays ended with an earthquake three days later - after which the "symptoms" promptly disappeared.
Alexander von Humboldt, traveller, naturalist and climatologist, died 140 years ago today, on May 6th, 1859.