1. Aderholt, A. E.—Die Theorie des Regenbogens in fasslicher Darstellung (Jena, 1858). [Especially good for diagrams of the caustics associated with the rainbow.]
2. Aichi, K., and A. Tanakadate—Theory of the Rainbow Due to a Circular Source of Light, Philosophical Magazine (6), VIII (1904), 598–610. [This material, amplified, is found also in Journal of the College of Science, Imperial University, Tokyo, vol. XXI (1906), article 3.]
3. Airy, Sir George Biddell—On the Intensity of Light in the Neighbourhood of a Caustic, Transactions of the Cambridge Philosophical Society, VI (1838), 379–403, VIII (1849), 595–600. [Airy’s classic paper on the rainbow.]
4. Babinet, Jacques—Mémoires d’optique météorologique, Comptes Rendus, IV (1837), 638–48. [Describes his method for observing supernumerary arcs experimentally.]
5. Billet, Félix—Études expérimentales sur les arcs supernuméraires des onze premiers arcs-en-ciel de l’eau, Comptes Rendus, LVI (1863), 999–1000, LVIII (1864), 1046. [Brief reports on his extension of the work of Babinet and Miller.]