346 DR c. B. PLOWRIGHT ON SILVER THAW AND GLAZED FROST. 
IX. 
ON THE SILVER THAW AND GLAZED FROST 
OBSERVED AT KING’S LYNN, 20-21st DECEMBER, 1901. 
By C. B. Plowright, M. D. 
Read 28tli January , 1902. 
The phenomenon of a glazed frost was well observed at King’s 
Lynn and its neighbourhood, on 20th and 21st December, 1901. 
For three or four days preceding Friday, 20th December, we had 
a succession of frosty nights, and more or less sunny days without 
either snow or any appreciable amount of rime frost. The roads 
in the country were frozen hard, but they were perfectly dry, free 
from ice, and not in the least degree slippery. On the afternoon of 
the 20th I drove through the village of Castle Rising, reaching 
home about half-past four ; the roads were then hard and good, and 
the horse did not require roughing. Soon after this a gentle damp 
wind sprang up from the south-west. About six o’clock I had 
occasion to walk a short distance in the town, when to my 
surprise I found the streets had become so slippery as to be dan- 
gerous for ordinary pedestrians. Not only were the pavements 
extremely slippery, but the roadways were even worse, whether 
paved with granite cubes or macadamised. A little later a gentle 
rain began to fall which rendered the silver thaw more noticeable 
still. The suddenness with which the hard dry roads became almost 
impassable sheets of ice astonished every one ; the change taking 
place within an hour, probably in half that time, and this too before 
any rain actually fell. The drivers of vehicles did not realise the 
state of the roads in the dusk until their horses slipped and fell. 
People who drove into Lynn from the country during the afternoon 
found that they could not return without having their horses 
roughed. The macadamised roads were far worse than those streets 
paved with granite setts or rounded pebbles. One of our main 
