On this day, 377 years ago, on September 1, 1648 (July 14, 1648 in the lunar calendar), French theologian, mathematician, and music theorist Maran Mason passed away. Marin Mersenne (September 8, 1588-September 1, 1648) was a French theologian, mathematician, and music theorist. Mason entered the monastery in 1611 and became a French Catholic Minima priest. In 1626, he turned his monastery in Paris into a meeting place for scientists and a center for exchange and information, called the "Mason College". He maintained regular correspondence with the greatest mathematicians of his generation and was a good friend of Fermat, the prince of amateur mathematics. Mason edited the works of several Greek mathematicians and discussed topics in them, especially the Mason prime number, and discussed it in the Cogitataphysico-mathe-matica published in 1644. His book "Harmonie Universelle" is a precious historical material recording contemporary musical instruments. Mason died in Paris on September 1, 1648. Comments: Mason numbers and Mason primes are named after him