25-MAY-1555:- Death Of Gemma Frisius,Dutch Physician, Mathematician and Inventor.

Gemma Frisius 
(December 9, 1508 – May 25, 1555), was a Dutch physician, mathematician,cartographer, philosopher, and instrument maker. He created important globes, improved the mathematical instruments of his day and applied mathematics in new ways to surveying and navigation.

Frisius was born in Dokkum, Friesland (present-day Netherlands), of poor parents who died when he was young. He moved to Groningenand studied at the University in Leuven beginning in 1525. He received the degree of MD in 1536 and remained on the faculty of medicine in Leuven for the rest of his life. His oldest son, Cornelius Gemma, edited a posthumous volume of his work and continued to work with Ptolemaic astrological models.

While still a student, Frisius set up a workshop to produce globes and mathematical instruments. He became noted for the quality and accuracy of his instruments, which were praised by Tycho Brahe, among others. In 1533, he described for the first time the method of triangulation still used today in surveying. Twenty years later, he was the first to describe how an accurate clock could be used to determine longitude. Jean-Baptiste Morin (1583–1656) did not believe that Frisius' method for calculating longitude would work, remarking, "I do not know if the Devil will succeed in making a longitude timekeeper but it is folly for man to try."

Frisius created or improved many instruments, including the cross-staff, the astrolabe, and the astronomical rings. 

Frisius died in Leuven at the age of 46. According to an account by his son, Cornelius, Gemma died from kidney stones, which he had suffered from for a minimum of 7 years.

A lunar crater has been named after him.