BEDS, BENCHES AND WALKS 157 



soil in place. In time, the constant addition 

 of manure raises the soil in these beds so 

 that they become in reality raised beds. 

 Board or plank curbs are rarely satisfactory, 

 as the moisture of the soil on one side causes 

 them to warp. The most satisfactory and 

 economical curbs are made of concrete, 

 which is heavily reinforced with iron rods 

 when it is poured. 



