238 THE PEACH ASD SHCTAEIHE. 



and obndnfition. It isfnot needful here and now to go mnoh further into 

 these somewhat difScult matters, though it was necessary to say so much 

 by way of warning. For if these principles are sound, they explain » 

 good deal that is often very puzzling and distressing, especially to 

 amateur cnltiTators, whom we are most anxious to guide and instruct in 

 this series of manuals. Not a few of these may hasten to build 

 glass houses for their peaches; many have, in fact, already done so 

 and fancy themselves quite safe. The year 1877 showed many that this 

 was by no means the case. Not a few unheated orchard houses were 

 almost as bare of fruit as the open walls that season. And the same 

 houses were wrecked again the same year by the intense frost of from 

 ISdeg. to 17deg. that ushered in the 1st of April, The diversity of 

 experience in regard to the protecting power of glass houses has seemed 

 like an enigma or a game of chance to not a few. Here a house has 

 been frozen, though close by another has escaped unhurt. The foregoing 

 epitome of the principles or laws of cooling explains these mysteries. 



In general terms, the larger the house the greater its power of con- 

 serving heat. Much also depends on the state of things at the start. 

 A grate full of coals bums longer than a few embers; so unheated 

 houses, shut up early in the afternoon, and filled to repletion with solar 

 heat, will take longer to cool than those left open till the sun has set, and 

 then closed with a temperature little, if at all, superior to the outside 

 air. No doubt this wider difference between the internal and external 

 atmospheres intensifies the energy and adds to the rapidity of the ex- 

 changes between the two ; but there being a far larger store of heat to 

 draw upon, it takes longer time to reduce the inside temperature to the 

 level of the external air. And in this matter time is everything. During 

 clear nights, when the danger from frost is greatest, the gain of an hour 

 or so in the equalisation of the two temperatures may save the crop. 



As a rule, the cultivator may calculate on having his houses filled with 

 heat by day. Of course, in duU weather this source of supply is not 

 available, and it is needful to save every degree of heat with miserly care ; 

 but dull days are mostly succeeded by dull nights, and these are safe. 

 It is the clear nights, when the whole atmosphere from bank to sky is 

 robbing the peach house of its heat, that the danger of freezing the 

 blooms is imminent. And the readiest antidote is also one which costs 

 nothing — a house full of heat, secured by early closing. 



The next simplest way of conserving warmth is by shutting it in. 

 The glass does this to some extent ; being transparent, however, it offers 

 but a feeble barrier to the radiation of heat into the open sky. Place an 

 artificial cloud over the glass in the form of a covering of felt, a mat, a roll 

 of. reeds or straw, and the loss of heat is at once arrested. True, radia- 



