92 THE ART AND PRACTICE OF LANDSCAPE GARDENING. 



Temporary copings are of great utility, especially during the 

 prevalence of late spring frosts. The heat accumulated in the 

 materials of the wall during the day is abstracted whenever the 

 air is colder than the wall. The cold air coming in contact with 

 the surface of the wall becomes heated, and consequently lighter ; 

 it then ascends, and the heat is lost so far as vegetation is con- 

 cerned. Broad copings obstruct the free ascent of warm air, which 

 then is longer retained where it is wanted on the surface of the 

 wall. The young shoots of vines may often be seen cut off by 

 frost as far as they have pushed beyond 9 in. coping boards, whilst 

 all the shoots that are under shelter of the boards are safe. 



A very good temporary coping is obtained by building in the 

 wall pieces of i % in. galvanised iron tubing, about 6 ft. apart, in 

 which can be placed iron rods projecting i ft. beyond the wall, 

 having a pin at the outer end. On this support, in the spring, 

 are placed 1 2 in. light boards, which are retained there so long as 

 necessary. Netting can also be suspended from these rods if it 

 be required to protect the fruit against frost, birds, or wasps. 



Feet. 



The sides of a square containing I acre are 20871 

 .. .. ,, 2 295-16 



. 3 3 6l> 5 



4 >i 4 r 7'54 



Feet. Feet. 



The sides in the proportion of 5 to 3 of a parallelogram are, for I acre, 269-45 x 161-67 

 ,, 2 381-03x228-63 



,, ,, 3 466'7ox28o'02 



.. , 4 



