70 QN THE CONSTRUCTION OF WALLS. 



should ever be suffered to fall upon them, if it can pos- 

 sibly be avoided. All the moisture which they stand 

 in need of they will freely imbibe from the atmos- 

 phere. 



In concluding these observations on the construction 

 of walls, it must be further observed, that, in addition to 

 the surface of a vine wall being as smooth as possible, 

 it ought, also, to be a true perpendicular, and the wall 

 itself to run in a straight line. These qualities are 

 necessary to ensure an equal distribution of solar heat 

 on its surface, and also an exemption from the increased 

 action of violent winds, which is sure to be generated 

 in some way or other, if the wall be built otherwise 

 than in a straight line. 



