1. There is a German translation: "Ostwald's Klassiker der Exakten Wissenschaften", No. 192, and one in French: "Åuvres Complètes de Christiaan Huygens", 18, published by the Société Hollandaise des Sciences (1934).
2. "Åuvres Complètes", 18, 635.
3. "History of the Inductive Sciences", 2, 59 and Chap. v.