352 Proceedings of Royal Society of Edinburgh. [sess. 
formation of dew bows is a multitude of minute drops of nearly 
the same size, and of so small a diameter that the sphericity is not 
appreciably disturbed. Here we must suppose that the impact 
of the drops on the ground itself, or on the drops already lying 
there, was so extremely gentle that it did not break through their 
surface- films. The well-defined character of the bows observed at 
distances of 10 or 20 yards from a dim gas lamp proves at once a 
great uniformity in the size of the drops, and a practically in- 
numerable multitude of them. The only meteorological conditions 
under which such uniformity could be attained are what we have 
already described, viz., a calm, still, foggy air, permitting the fog 
particles to settle gently down upon the ground with a terminal 
speed of, at most, an inch per second. 
December 23. — Since the above note was read, we have heard 
that the phenomenon was observed by some of the night police- 
men on the two previous evenings of November 9 and 10, 
while the fog was still dense, as well as on the 11th, when we 
noticed it. The bows are said to have been much brighter on 
the last night than on the two previous ones ; and on that night 
to have increased in brilliancy towards morning. 
