CONCRETE CONSTRUCTION 243 



came the most stable part of the structure. 

 Concrete is practically the only material now 

 used for the foundations and walls of com- 

 mercial greenhouses, and to a great extent 

 it has displaced masonry for private 

 greenhouses. 



At present cement is almost universally 

 handled and shipped in cloth or paper sacks 

 holding 95 pounds. It is often spoken of, 

 and is sometimes quoted by the barrel, 'this 

 now meaning simply four sacks, or 380 

 pounds. As a rule, the most satisfactory 

 form in which to buy cement is in cloth sacks. 

 The sacks may be returned when empty, and 

 if not torn a credit of about 10 cents each 

 may.be realized. 



Sand. Sand, to give the most satisfac- 

 tory results, should be free from clay or or- 

 ganic matter, and rather coarse. Very fine 

 sand will require a greater proportion of 

 cement and as, a consequence the concrete 

 will be more expensive. In a small way, 

 sand that contains some organic material 

 may be washed and thus made satisfactory, 

 but it is an expensive process. 



