186 HOAR FROST. 



able on a dry frosty day, a day even of the keenest 

 frost, than on those raw days which are not exactly 

 either frost or thaw, or even when thaw comes 

 slowly, and the surface is covered with melting 

 snow and ice. The hard ice and unmelting snow 

 in the clear frosty day affect the air very little, 

 whereas on the raw day, and when it thaws partially, 

 the air is loaded with moisture, which takes the heat 

 out of it : and as, on such days, there is seldom any 

 direct sunshine to assist in dispersing the moisture 

 up into the air, it hangs in the lower strata like a 

 heavy fog, and abstracts heat from the human body, 

 and forms hoar frost upon the hair and clothes : and 

 whenever the temperature sinks a little, the water 

 is deposited and crystallized upon every solid sub- 

 stance, and the more so the more slender the sub- 

 stance is, so that the grass and bushes and the twigs 

 of the trees are frosted over with spiculae of ice, 

 which have a very pretty but very cold appearance. 

 Those hoar frosts are most frequent in the autumn, 

 before the waters be so far cooled down as that ice 

 or dry frost is found. They sometimes occur late 

 in the spring and in cold districts occasionally even 

 in the summer. 



If in the latter part of the season those hoar 

 frosts, or white frosts, " hold," by a continuance of 

 the cold atmosphere near the surface, they generally 

 end in dry or black frost, and are followed by cold, 

 but healthy and hearty winter weather. But if that 

 air near the surface be warmed by any cause, so that 

 the frost " gives way," or, as it is called in some 

 parts of the country, " leaps," then, if the cause of 

 that be general, rain is the immediate consequence, 

 even though the general progress of the season be 

 such as ultimately to lead to black frost, and a heavy 

 fall of snow. 



It may seern a little contradictory that temporary 

 local heat should produce cold, but it is nevertheless 

 true, in that as well as in other cases. How soon 



