T. B. Harding. — On Bainhoivs. 481 



Art. LV. — A Further Note on Bainhoius. 



By T. B. Harding. 



Communicated by B. G. Harding. 



[Bead before the Wellington Philosophical Society, 26th July, 1893.] 



Plate LIV. 



On Friday, 16th June, 1893, at about 3.30 p.m., I had an 

 excellent view of a peculiar and splendid double rainbow. It 

 formed in appearance a semicircle, and a quadrant sprang from 

 the ends of the same chord. It was first seen from the 

 Hyderabad Eoad, leading from the Spit tovv'ards the Town of 

 Napier, and close by Battery Point, Scinde Island being on 

 the left hand, and concealing the greater portion of the arch. 

 At this point the two bows did not appear to cross at the ter- 

 minals, but to unite on the end of the chord. The phenomenon 

 continued visible for fully half an hour, or until I was a good 

 distance on the Taradale Eoad. The chord appeared 4° or 5° 

 above the horizon. Both bows were of unusual brilliancy 

 and, as I reached a point where Scinde Island did not inter- 

 vene, completeness. The bows gradually approached each 

 other as the sun drew^ nearer the horizon. Between myself 

 and the sun there lay an extensive sheet of water, the inner 

 harbour of Napier, perfectly calm and reflecting the sun as 

 from the surface of a mirror. The first thing that struck me 

 on seeing the phenomenon was that the two bows were not 

 concentric, as would have been the case with an ordinary 

 primary and secondary bow. The next was that they were 

 both primaries ; and the question occurred, How is this ? 



On turning towards the sun I saw at once that there were 

 practically two of them — one a few degrees above the horizon, 

 and the other just as much below it, apparently shining up- 

 ward through the water. The explanation was at once evi- 

 dent, and the phenomenon became of much interest to me. 

 The reflected sun gave a bow of more than half a circle, the 

 true sun one of less, and the two arcs actually crossed each 

 other well above the horizontal line. The lower bow appeared 

 to be the arc of a much larger circle than the upper one, but 

 this was probably owing to atmospheric causes, which, as is 

 well known, give an enlarged appearance to objects near the 

 horizon. It is probable they were of the same diameter, with 

 some 2(P difference of centres. The best effect was observed 

 from the causeway on the Taradale Eoad, where the Town of 

 Napier could be seen on the left hand, clear of Scinde Island. 



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