Bartholinus, Erasmus

Exactly 300 years ago (1669), Nicolaus Steno discovered the law of constant interfacial angles in quartz, and Erasmus Bartholinus discovered the double refraction of light in calcite about the same time, Robert Boyle (1661) defined the concept of chemical elements by qualitative mineral analyses. 

Book iv of B is on chemical principles. In 1668 Duhamel met Boyle in England and two chapters in the second edition (1669) of B contain experiments on the elasticity of air and refer to Boyle s work on it. C refers to many modern authors, including Boyle, Bacon, Gilbert, Willis, Hooke, Gassendi, Descartes, Pascal, Galileo, Torricelli, Guericke, Tachenius, and Erasmus Bartholinus. Boyle quotes Du Hamel s praise in C of his own Experiments and Observations touching Coldy 1665. Duhamel was the first Secretary of the Academic Royale des Sciences (1666-97). 

Thomas Bartholin (Bartholinus) (Copenhagen, 20 October 1616-Hagested, 4 December 1680) was professor of mathematics (1647) then anatomy (1648-61) in the University of Copenhagen, and King s physician (1670) he wrote De luce animalium, Leyden, 1647 (see Vol. II, p. 549). His brother Erasmus Bartholinus discovered the double refraction of light in Iceland spar. ... 

The phenomenon of double refraction, firstly observed for the calcite crystals by Erasmus Bartholinus since 1669 is remarkable by the fact that... 

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