Bernard Brunhes was a French

French people

The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...

 geophysicist

Geophysics

Geophysics is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and...

 known for his pioneering work in paleomagnetism

Paleomagnetism

Paleomagnetism is the study of the record of the Earth's magnetic field in rocks. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of...

, in particular, his 1906 discovery of geomagnetic reversal

Geomagnetic reversal

A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse...

. The Brunhes–Matuyama reversal is named for him.

Brunhes was educated at the École Normale Supérieure

École Normale Supérieure

The École normale supérieure is one of the most prestigious French grandes écoles...

 in Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

, from which he graduated as an agrégé

Agrégation

In France, the agrégation is a civil service competitive examination for some positions in the public education system. The laureates are known as agrégés...

qualified in physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

. Appointed at Université Lille Nord de France

Université Lille Nord de France

The University of Lille -Nord de France , located in Lille, France, is a center for higher education, academic research and doctoral studies located over multiple campuses in the Academie de Lille....

, he taught physics and electrical engineering at École centrale de Lille

École Centrale de Lille

Located in the campus of the University of Lille in France, École Centrale de Lille is a renowned Graduate Engineering school, with roots back to 1854 as the École des arts industriels et des mines de Lille, re-organised in 1872 as Institut industriel du Nord.It is one of the Centrale Graduate...

 from 1893 to 1895.

In November 1900, he was appointed as head of the Puy-de-Dôme

Puy-de-Dôme (mountain)

Puy de Dôme is a large lava dome and one of the youngest volcanoes in the Chaîne des Puys region of Massif Central in south-central France. This chain of volcanoes including numerous cinder cones, lava domes, and maars is located far from the edge of any tectonic plate. Puy de Dôme is located...

 Observatory, built on an extinct volcano in the Auvergne

Auvergne (région)

Auvergne is one of the 27 administrative regions of France. It comprises the 4 departments of Allier, Puy de Dome, Cantal and Haute Loire.The current administrative region of Auvergne is larger than the historical province of Auvergne, and includes provinces and areas that historically were not...

 region of France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, where he worked until his death in 1910.

It was during his time at the observatory that he made the crucial observation that led to his discovery of geomagnetic reversal. In 1905, he found that rocks in an ancient lava flow at Pontfarin in the commune of Cézens

Cézens

Cézens is a commune in the Cantal department in south-central France.-Population:-References:*...

 (part of the Cantal

Cantal

Cantal is a department in south-central France. It is named after the Cantal mountain range, a group of extinct, eroded volcanic peaks, which covers much of the department. Residents are known as Cantaliens or Cantalous....

 département) were magnetised in a direction almost opposite to that of the present-day magnetic field

Magnetic field

A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

. From this, he deduced that the magnetic North Pole of the time was close to the current geographical South Pole

South Pole

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...

, which could only have happened if the magnetic field of the Earth had been reversed at some point in the past. He was correct, though it took another 50 years before his theory was fully accepted by the scientific community.