GZNESAL OTJLTIVATION. 226 



than the coldont. In protecting our peaoh trees we wage war less against 

 an aotive enemy attacking them from witheut than in favour of our beat 

 ally, heat, already fighting from withia to save our trees. In a word, 

 the object of the cultivator is to protect from the loss of heat already 

 stored in the trees, the brick wall, and the ground contiguous to both, 

 from Tjjthin. We have been careful to lay down the general principles of 

 efficient protection, as it Shows the importance of the old system, once so 

 general, in unfavourable localities, but now, without any valid reason, 

 almost obsolete, that of heating peach walls when necessary with flues or 

 hot- water pipes. A very small addition of heat to walls on a frosty night 

 proved sufficient to protect peach trees in bloom from destruction, inas- 

 much as the heat was applied exactly where it was needed to the trees on 

 the walls to which they were so closely attached. Thus it often happened 

 on flued walls that while the blooms that hugged the wall escaped those 

 that stood out from it were destroyed. The same thing still happens 

 with unSued walls, proving that the wall and the trees themselves are 

 the sources of heat. These flues added comparatively little to the ex- 

 pense of the walls, as, though flued walls must be thicker than those 

 that are unflued, the large proportion of hollow spaces reduces the 

 number of bricks. Neither did they cost much for fuel, for one never 

 thought of lighting the fires until the trees were nearly in blossom, nor 

 then unless when severe frosts or bitingly cold winds rendered them 

 necessary. 



In mild seasons, for example, no fires would be needful till after the 

 middle of March, and gentle fires from that period till the end of the 

 month ; a few perhaps in April, and two or three during the annual cold 

 snaps about the middle of May, would almost certainly save myriads 

 of fine peaches, nectarines, plums, and pears that would otherwise 

 utterly perish. 



No doubt there was some risk in the use of flued ^r^'Us, and gre^t 

 dangers in their abuse. They required care and skiU in their working, 

 and so does almost everything else. But with careful use and the 

 employment of no more heat than was needful,, there was no reason why 

 flues should either half roast the trees or cause them to fall a prey to 

 red spider before their leaves had half performed their function. 



Besides, all the evils connected with flues were abolished by running 

 a few hot-water pipes along the bases of honey-combed or pigeon-holed 

 walls. The heat was then perfectly safe, and by the aid of a tew 

 evaporating pans could be made as moist as desired. The mere hollow- 

 ness of the walls when unheated gave them a decided advantage over 

 solid walls, as the air inclosed parted with its heat slowly as the 

 external surface of the bricks was robbed of its heat by the external 



