CATALOGUE. — PHYSICAL OPTICS. 



309 



Makes the angles 41° so' and si 55' for the usual rain- 

 bows : the ternary and quaternary would be 40° ao' and 45° 

 »3' from the sun. 



A red rainbow. A. P. I7O8. H. 109. 

 Thoresby on a lunar rainbow. Ph. tr. 1711. 

 XXVII. S20. 



With all the colours. 



Langwith on a In'perbolic rainbow on the 



"ground. Ph. tr. 1721. XXXI. 229- 

 Sturmii iridis admiranda. 

 Pemberton's optical porisms. Ph. tr. 1723. 



XXXir.245. 

 Smith's optics. 

 Jo. Bernoulli. Op. IV. 197. 

 Celsius on a rainbow seen in Dalecarlia. A. 



P. 1743. H. 3.5. 

 Berthier on a singular rainbow. A. P. 1747. 



H. 52. 



On the banks of the Loire. 



Webb on an inverted iris on the grass. Ph. 



tr. 1751. 248. 

 •Edwards on a rainbow after sunset. Ph. tr. 



1757. 293. 

 Legentil on two singular rainbows. Ph. tr. 



1757. 39. 

 Kotelnikow on the iris. N. C.'Petr. Vir.252. 

 The tertiary iris, after 5 reflections, would be very broad, 

 and partly covered by the secondary. 



Bergmann on the rainbow. Schw. Abh. 1759. 



231. 

 Boscovich on the secondary rainbow. S. E. 



III. 321. 



In order to avoid a difficulty deduced from the imaginary 

 fits of reflection, is obliged to suppose the drops imperfectly 

 spherical. 



Boscovich. Hamb. Magaz. X. 531. 

 Mallet on the rainbow. Schw. Abh. 1763. 



£39. 

 Singular rainbows. Coll. Acad. VI. 253, 265, 



286, 296, 299, 356, 433. 

 On the ground, red, and lunar. 



Sejour on alunar rainbow, A. P. 1770. H. 22. 



White. 



Roz. II. 296. 



A third iris between the common ones, not concentric 

 with them. Probably by reflection. 



An entire rainbow. Roz. III. 4l6. 



A lunar rainbow. Roz. X. 81. 



Dicquemare on a distorted iris. Roz. X. 136. 



Probably by refraction. 



E. M. Physique. Art. Arc-en-ciel. 

 Tunstall on lunar irides. Ph. tr. 1783. 100. 

 L'Abbe P. sur Tare en ciel. 8. Par. 1788. 



R.S. 

 A lunar rainbow. -Roz. XXXIV. 60. 

 Hellwag N. Deutsch. Merkur. 1790. ii. 420. 

 Sturges on two rainbows. Ph. tr. 1793. 1. 



One by reflection from the sea. 

 A lunar rainbow. Ph. M. XI. 96. 

 Bouvier on a lunar rainbow. Journ. Phy». 



LVII. 472. 

 Alunar rainbow. Gilb. XI. 480. 



Seen by Professor Seyfferof Gottingen. The red, green, 

 orange, and violet colours were very lively and distinct. 

 The editor remarks that this phenomenon is not so rare as is 

 sometimes supposed, for that Mr. Alfeld has collected ac- 

 counts of 30 lunar rainbows which had been seen before 

 1 7 SO. This observation is only of consequence as it tends 

 to destroy the opinion of the existence of a diflFerence in the 

 colours of the lunar and solar rainbows. 



Theorim. The angular distance of the primary and 

 secondary rainbow being given, if a unicuspidate and a bi- 

 cuspidate epicycloid be described in a circle, touching it in 

 points at the given angular distance ; the distance of their 

 point of intersection from the centre will be to the tacliusat 

 uniiy to the index of refraction. Y. 



Double Refraction. 



Bartholin on Iceland crystal. Ph. tr. I67O. 



V. 2039- 

 *HugensTraite de la lumifere. 

 On Iceland crystal. A. P. I. 186. 

 Lahire on Iceland crystal. A. P. 1710. 

 Beccaria on the double refraction of roqfc 



crystal. Ph. tr. 1762. 486, 



