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De Groot, Jan Cornets (NNBW gives his name also as Johan Hugo de)

1. Dates
Born: Kraayenburg (between Delft and The Hague, 8 March 1554
Died: Delft, 3 May 1640
Dateinfo: Dates Certain
Lifespan: 86
2. Father
Occupation: Aristocrat
Apparently a Delft patrician.
It seems clear from the details of his life that de Groot inherited sufficient wealth to live well. Nothing is said; I'll call the family affuent.
3. Nationality
Birth: Dutch
Career: Dutch
Death: Dutch
4. Education
Schooling: Leiden; Douai, M.A.
He enrolled in the University of Leiden when it was opened in 1575.
M.A. and M.Phil at Douai.
In 1596 he was awarded the doctorate of law by the University of Leiden. I feel certain that this was honorary, and I won't list it.
5. Religion
Affiliation: Obviously Calvinist
6. Scientific Disciplines
Primary: Mechanics
Subordinate: Optics
De Groot was a distinqueshed amateur scientist, and best known for the experiment he performed with Stevin, published in Stevin's Waterwicht (1586), in which they proved that lead bodies of different weights in falling traverse the same distance in the same time.
He was also knowledgable in optics.
7. Means of Support
Primary: Personal
Secondary: Governmental Position, Patronage
He was a counselor of Delft, and from 1591 to 1595 was one of the mayors. Without knowing the details, I am convinced that these positions, the functions of patricians, were also their perquisites and carried salaries.
He was a curator of the University of Leiden, 1594-1596.
After 1617 he served as adviser to the Count of Hohenlohe.
It is impossible to make much out of de Waard's miserable sketch in NNBW, but I do not see how one can interpret the details of de Groot's life without assuming personal wealth. He is called a patrician of Delft.
8. Patronage
Type: Aristocracy--See Above
9. Technological Involvement
Type: Hydraulics
With Stevin in building windmills on contract.
10. Scientific Societies
Memberships: None
He was acquainted with the best minds in the Netherlands.
He collaborated with Stevin in the performance of mechanical experiments and in the construction of windmills.
He also befriended Ludolph Van Ceulen, on whose behalf, he translated Archimedes' Measurement of the Circle into Dutch. In 1586, Ceulen submitted to him his approximation of pi to 20 decimal places.
  1. Waard, "Groot,", Nieuw Netherlandsch biographisch Woordenboek, 2, (1912), cols. 528, 529. CT1143 .M72 RF Not consulted: The Principal Works of Simon Stevin, Amsterdam, 1955-1966, esp.
  2. vols.I,V. Q155 .S78 SWAIN LIBRARY Surprisingly, there is just not a lot on de Groot. De Waard's sketch is impossibly opaque.
Compiled by:
Richard S. Westfall
Department of History and Philosophy of Science
Indiana University

Note: the creators of the Galileo Project and this catalogue cannot answer email on geneological questions.

1995 Al Van Helden
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