ON RAINBOWS. 665 



but also beyond that of the illuminated fog, was a pale, white, lumi- 

 nous circle, complete except at the point where it was cut through by 

 the shadow. As I walked out into the fog, this curious halo went in 

 advance of me. Had not my demerits been so well known to me, I 

 might have accepted the phenomenon as an evidence of canonization. 

 Benvenuto Cellini saw something of the kind surrounding his shadow, 

 and ascribed it forthwith to supernatural favor. I varied the position 

 and intensity of the lamp, and found even a candle sufficient to render 

 the luminous band visible. With two crossed laths I roughly meas- 

 ured the angle subtended by the radius of the circle, and found it to 

 be practically the angle which had riveted the attention of Descartes 

 — namely, 41°. This and other facts led me to suspect that the halo 

 was a circular rainbow. A week subsequently, the air being in a simi- 

 lar misty condition, the luminous circle was well seen from another 

 door, the lamp which produced it standing on a table behind me. 



It is not, however, necessary to go to the Alps to witness this singu- 

 lar phenomenon. Amid the heather of Hind Head I have had erected 

 a hut, to which I escape when my brain needs rest or my muscles lack 

 vigor. The hut has two doors, one opening to the north and the other 

 to the south, and in it we have been able to occupy ourselves pleasantly 

 and profitably during the recent misty weather. Removing the shade 

 from a small petroleum-lamp, and placing the lamp behind me, as I 

 stood in either doorway, the luminous circles surrounding my shadow 

 on different nights were very remarkable. Sometimes they were best 

 to the north, and sometimes the reverse, the difference depending for 

 the most part on the direction of the wind. On Christmas-night the 

 atmosphere was particularly good-natured. It was filled with true fog, 

 through which, however, descended palpably an extremely fine rain. 

 Both to the north and to the south of the hut the luminous circles 

 were on this occasion specially bright and well-defined. They were, 

 as I have said, swept through the fog far beyond its illuminated area, 

 and it was the darkness against which they were projected which ena- 

 bled them to shed so much apparent light. The " effective rays," there- 

 fore, which entered the eye in this observation gave direction, but not 

 distance, so that the circles appeared to come from a portion of the 

 atmosphere which had nothing to do with their production. When 

 the lamp was taken out into the fog, the illumination of the medium 

 almost obliterated the halo. Once educated, the eye could trace it, 

 but it was toned down almost to vanishing. There is some advantage, 

 therefore, in possessing a hut, on a moor or on a mountain, having 

 doors which limit the area of fog illuminated. 



I have now to refer to another phenomenon which is but rarely 

 seen, and which I had an opportunity of witnessing on Christmas-day. 

 The mist and drizzle in the early morning had been very dense ; a walk 

 before breakfast caused my somewhat fluffy pilot dress to be covered 

 with minute water-globules, which, against the dark background under- 



