Dr W. Scoresby on Prismatic Colours in Dew Drops. 49 



distance. I then procured a table, and by placing an otto- 

 man on it, I found, when standing on the summit, that I 

 was now high enough to view the leaves distinctly. Look- 

 ing down at an angle of from 60° to 70°, from a horizontal 

 plane, I saw distinctly the whole surface of a leaf thickly 

 bespangled as with the most exquisitely coloured gems of 

 varied colours, — every colour of the rainbow being seen at 

 the same view, though in somewhat irregular disposition, on 

 the same leaf and at the same moment, and whilst, by a 

 slight movement of the head, when still observing the appear- 

 ances, the colours were made to shift and change as by a 

 magical illusion. Scarcely anything in light and colour 

 could exceed the brilliant variety and beautiful play of the 

 colours as thus viewed from a small elevation. 



On some leaves I found a disposition towards the prismatic 

 arrangement in the various colours ; and, ultimately, after 

 several trials, I found a small row of very globular drops on 

 the horizontal part of a leaf, presenting, in regular succes- 

 sion, this series of colours, — pale blue, sulphur yellow, 

 orange red. On another leaf, an extended deposit of minute 

 dew drops exhibited a like variety and arrangement, in which 

 all the colours of the spectrum were exhibited, and very 

 nearly in their proper order. The deviations from the 

 proper order are clearly ascribable to defect in perfect sphe- 

 ricity. 



In the former paper, the circumstances under which the 

 dew was deposited — being in excessive profusion, probably, 

 so as to overrun the surface on which deposited — occasioned 

 the phenomena to be best observed in drops pendant from 

 minute blades of grass; but here the drops lay, as most 

 usually is the case, deposited chiefly on the upper surfaces 

 of the grass and plants. 



2. The second variety of these phenomena, which I have 

 here to describe, consisted in the exhibition of prismatic 

 colours in the minute globules of dew deposited on gossamer. 



The colours, as observed in the dew on the gossamer web, 

 I have found to be far more splendid, in respect to the 

 immense aggregation of brilliant coloured points, than in 

 any other form in which the phenomena had been observed. 



VOL. L. NO. XCIX.— JANUARY 1851. D 



