Version of Papin's digester.

In engines, the Papin digester or Bone digester was a type of pressure cooker invented in 1679 by French engineer Denis Papin.

Steam engine
Early versions resulted in explosion, owing to the extreme pressures. Late version fixed this problem by adding on steam release valve. It is said that by watching the steam release valve bob up and down that Papin conceived of the design of the steam engine, the Papin engine, as outlined in his 1690 memoir "A New Method to Obtain Very Great Motive Powers at Small Cost." [1]

See also
● Timeline of engine development

References
1. (a) Papin, Denis. (1690). “A New Way to Obtain Very Great Motive Powers at Small Cost” (Nova Methodus ad Vires Motrices Validissimas levi Pretio Comparandas). Acta Eruditorum, anno, Aug., pgs. 410-14.
(b) Muirhead, James. (1859). The Life of James Watt, (English translation: Ch. XI, Denys Pain: His memoir of 1690, Section: A New Way to Obtain Very Great Motive Powers at Small Cost”, pgs. 131-42). London: John Murray.

External links
● Steam digester – Wikipedia.