AND ITS CONGENERS. 209 



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 de- 

 pending for the most part on the direction of the wind. 

 On Christmas night the atmosphere was particularly 

 favourable. 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 enabled them to shed so much apparent light. 

 The "effective rays," therefore, 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 pro- 

 duction. 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 the nap of my somewhat fluffy pilot- 

 dress to be covered with minute water-globules, which, 



