Steno was born into a wealthy Lutheran family in Copenhagen, Denmark. He studied medicine in Copenhagen, Leiden and Amsterdam, where he discovered the excretory duct of the parotid gland. After travels through France, Austria and Hungary, he became physician to the Grand Duke Ferdinand II in Florence, Tuscany. In 1666, he dissected the head of a large shark at the Duke's request and concluded that glossopetrae found in rocks are identical to shark teeth. He continued intensive geological observations, which culminated with his greatest work, De Solido Intra Solidium Naturaliter Contento Dissertationis Prodromus (Forerunner of a Dissertation on a Solid Naturally Contained within a Solid), often simply called the Prodromus. This was a bold statement of the organic origin of fossils and fundamental principles of stratigraphy, published in 1669. Although now regarded as a geological masterpiece, the conclusions of Prodromus were not generally accepted until the following century.
His earlier conversion to Catholicism in 1667 began to produce personal conflict with his geological observations, and shortly after writing the Prodromus, Steno lost all interest in geology. His geological career, thus, spanned three short years. Although he returned to Denmark for a few years, he was not happy, and moved back to Florence, where he became a priest in 1675. In 1677 he was appointed titular Bishop and spent the rest of his life involved with missionary work in northern Germany.
Niels Stensen (also Nils or Steensen) was born to a wealthy family of Lutheran goldsmiths in Copenhagen. His name means literally Niels, "Son of Rocky" (sten = stone or rock). He studied medicine first in Copenhagen then in the Netherlands at Leiden and Amsterdam. He became (1660-63) a celebrated anatomist and discovered the excretory duct of the parotid gland (salivary gland in front of ear), which is today known as "Stensen's duct." He sought a university position in Copenhagen, but was turned down. At that time, faculty positions went to relatives of the head professor. Thus, this famous native son was rejected in his own country.
After a time in France, he travelled in Austria and Hungary. In 1666 (or 1665) he became physician to the Grand Duke in Florence, Tuscany (Italy). Ferdinand II of Medici was wealthy and gave Steno considerable freedom. His first contact with geology came at this time (1666), when he dissected the head of an unusually large shark (see textbook p. 35-37). He concluded that "glossopetrae" (fossil teeth) were in fact identical to shark teeth. His 1667 report is a timid, cautious appendix to a treatise on muscles; it is nonetheless clear that he understood the organic origin of fossils.
Steno then began intensive geological study and travel in Tuscany. He visited quarries, mines, and caves; he saw the famous Carrara Marble, Appenine Mountains, Arno River, and coastal lowlands. In the midst of this, he was converted to Catholicism in 1667. He also received requests from the Danish King to return to Copenhagen. He knew he could not resist the king for long, so in 1668 he wrote his most important work, one which is now regarded as a classical geological masterpiece--De Solido Intra Solidium Naturaliter Contento Dissertationis Prodromus (Forerunner of a dissertation of a solid naturally contained within a solid), often now called simply the Prodromus.
Title page from Steno's
published in 1669.
The dissertation to follow this forerunner was never written. However, behind this obscure title is one of the most important geological publications of the Renaissance Era. It was a bold statement of the organic origin of fossils and how fossils came to be enclosed in rock layers. Steno enunciated the basic laws of stratigraphy.
Each stratum is deposited from fluid upon a solid subjacent surface--hard (solid) fossils may be incorporated into soft (loose) sediment at this stage.
Each stratum is laterally continuous and approximately horizontal.
Superposition (stacking) of strata takes place according to age.
Any deviation is due to later alteration--earthquake, volcano, etc.
Fossils are anatomically identical with parts of living organisms, particularly teeth, bones, and shells. Fossilization into crystalline material takes place over long passage of time; thus, many fossils must be as old as the general deluge. Steno interpreted all rocks in terms of deposition of sediment from fluid. He apparently knew nothing of granite or lava, which are not in Tuscany. He made few (if any) geological observations outside of Tuscany.
Prodromus includes a general geological history of Tuscany, the first time a written geological history was ever attempted. He presented a series of diagrams that show his clear understanding of stratigraphic principles. In addition he recognized the importance of running water in modifying the landscape. He envisaged six stages for the geological formation of Tuscany, which he thought might be global in occurrence.
Region entirely submerged, no fossil remains in strata.
Land uplifted as dry plains.
Land broken into mountains, ravines, and hills.
Submergence with valleys filled with fossiliferous sand.
Land reappears as broad plains.
Erosion of land by rivers into hills and valleys.
Catholic censors had to approve all scientific publications in Steno's time. The first censor, Viviani, was sympathetic and approved; however, the second censor delayed four months before approval. During this period, Steno lost interest, perhaps because of personal religious conflicts. The publication in 1669 ultimately was arranged entirely by Viviani.
Steno abandoned geology after only three years and returned to Denmark. He was professor of anatomy at the University of Copenhagen (1672-74), but was not happy. As a Catholic, he was uncomfortable in a Lutheran country. So he left again. He became tutor to the son of Grand Duke Cosmo III in Florence, and devoted himself increasingly to religious matters. Steno became a priest in 1675 and completely gave up science for the remainder of his life. In 1677, he was appointed titular Bishop of Heliopolis and Vicar Apostolic--actually he became the chief of Catholic missionary work in northern Germany. He was so consumed by this work that his health deteriorated, and he died at age 48. Steno was given saintly status by Pope John Paul II in 1988.
Based on the Prodromus, Steno is often considered the father of geology. However, his genius did not endure or develop fully; nor was he acceptable to his contemporaries, who did not believe in the organic origin of fossil teeth, bones, and shells. It took another century for the tremendous truth about stratigraphy and fossils in the Prodromus to become accepted. Two centuries passed before the importance of rivers finally was demonstrated in the western United States.
Danish geologists today are proud to claim Steno as a native son, in spite of the ironic facts that he was twice forced to leave his homeland and that he never practiced geology in Denmark. Steno is commemorated by the University of Copenhagen's "Steno geology student club" (see below). The Danish Geological Society awards a "Steno Medal" for high achievement in geology. This gold medal was begun in 1969, on the 300th anniversary of the publication of the Prodromus. The Steno Museum is located at the University of Aarhus--see title image.
Woodcut illustration of Nicolaus Steno.
Taken from the Steno Songbook
(Steno geology student club, 1973).