Sunrise- Shadows of Adam* s Peak in Ceylon. 33 



and form a bow. In every case the shadow and bow were 

 seen in front of land and never against the sky. The last 

 time, when the sun was pretty high, we saw the characteristic 

 peculiarity of the shadow. As a thin wreath of condensed 

 vapour came up from the valley at a proper height, a bow 

 formed round the shadow, while both seemed to stand up in 

 front of us, and then the shadow fell down on to the land, 

 and the bow vanished as the mist passed on. 



Here, then, was an unequivocal explanation of the whole 

 phenomenon. The apparent upstanding of the shadow was 

 simply the effect of passing mist which caught the darkness 

 of the Peak at a higher level than the earth, for when the 

 condensed vapour moved on, the characteristic bow disappeared 

 and the shadow fell to its natural plane on the ground. 

 When the mist was low, as on the two first occasions, the 

 shadow fell on the top as it were, and there was no appearance 

 of lifting, only the formation of a bow. 



The well-known theory of the bow is that light diffracted 

 in its passage between small water-globules forms a series of 

 bows according to the size of the globules, their closeness, 

 and the intensity of the illumination. Had the mist been so 

 fine and thin as merely to catch and raise the shadow, but 

 not to form a bow, there might have been some doubt as to 

 the origin of the appearance. Our fortune was in the un- 

 settled weather, which made the mist so coarse and close that 

 the unequivocal bow left no doubt as the true nature of the 

 cause. 



About an hour later the sun again shone out, but much 

 higher and stronger than before, and then we saw a brighter 

 and sharper shadow of the Peak, this time encircled by a 

 double bow. Our own spectral arms were again visible, but 

 the shadow was now so much nearer the base of the Peak, 

 and we had to look so much down on it, that there was no 

 illusion of standing up, and there were no dark diverging 

 rays. The inner bow was the one we had seen before; the 

 outer and fainter one was due to stronger light. 



The bows were all so feeble and the time so short, that the 

 author did not succeed in obtaining any sextant measure- 

 ments of the diameters of the bows ; but his thermometric 

 observations conclusively disprove any idea of mirage. At 

 6 a.m. the thermometer on the Peak marked 52° F., while at 

 Colombo the temperature stood at 74°*85. The difference of 

 22°* 85 is just about the normal difference in temperature due 

 to a height of 7352 feet. 



The Colombo figures were procured through the courtesy 

 of the Surveyor-General for Ceylon. They are got as fol- 



Phil. Mag. S. 5. Vol. 23. No. 140. Jan, 1887. D 



