222 CULTURE AND MANAGEMENT OF OAK. 



after the nurses have attained a size to be of service 

 to them. But, by not planting the oaks till the 

 Scots firs and larches are tall enough to yield mi- 

 mediate shelter, the plants will be protected from 

 the very first, not only from the violence of the 

 winds, but from the still more injurious frosts, which 

 often prevail late in spring, and early in autumn, 

 destroying incipient vegetation at the one season, 

 and killing the unripened shoots at the other. 



The manner in which the nurses will screen the 

 young oaks from the force of the winds, will be easily 

 understood by every reader ; but it may not appear so 

 evident how the frosts, which fall perpendicularly 

 downwards, can be warded off by the same means. 

 To explain this, it may be necessary to state, that 

 the deleterious effects of spring and autumnal frosts, 

 arise chiefly from the leaves being subjected to a 

 sudden change of temperature, from the freezing 

 chill of the night to the strong heat of the 

 rays of the morning sun. When the thaw takes 

 place gradually, the injury done is comparatively 

 insignificant. Several undoubted proofs of this 

 can be adduced. Agriculturists have found by 

 long experience, that their crops are never so much 

 hurt by frost, when the sun rises clouded, and rain 

 succeeds, as when the night is followed by a morn- 



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