TREATISE

ON LIGHT.

Wherein are explained

The causes of what happens to it

In REFLECTION and in REFRACTION.

And particularly

In the strange REFRACTION

OF ICELAND CRYSTAL.

original: "Cristal d’Islande." Known today as Iceland spar, this transparent variety of calcite was crucial to Huygens' discovery of the polarization of light because of the way it splits a single beam into two.

By C. H. D. Z.

These initials stand for Christiaan Huygens de Zuilichem. Huygens was a leading figure of the Scientific Revolution, known for inventing the pendulum clock and discovering the rings of Saturn.

With a Discourse on the Cause

OF GRAVITY.

GravityThe original French term 'pesanteur' refers to the quality of being heavy or the force that pulls objects toward the Earth; Huygens sought a mechanical explanation for this phenomenon.

A central circular woodcut emblem depicts a man, likely a traveler or a pilgrim, walking through a rural, hilly landscape with a staff in his hand and a pack on his back. The scene is enclosed within a thick wreath of leaves. To the right of the central emblem are two library or ownership stamps: a small, faint oval stamp above a larger, more distinct armorial stamp featuring a crowned shield with a cross and a motto.

At LEIDEN,

At the house of PIERRE VANDER AA, Bookseller.

1690.