278 MASONRY. 



When the wall is perforated by doors and windows, or 

 other openings, find the sum of their cubic feet by severally 

 multiplying their lengths and widths and thicknesses in feet 

 together, and deducting the whole from the cubic contents 

 of the wall, including the openings, before multiplying by 

 20 or 15, as above. 



Laths. 



Laths are 1J to 1 inches wide by 4 feet long, are usually 

 set J inch apart, and a bundle contains 100. 



