178 AGRICULTURAL ENGINEERING 



bridges. Stone and brick make desirable culverts, but the 

 convenience of handling and reinforcing concrete with steel 

 makes it very useful for culvert and bridge construction. 

 Vitrified Pipe and Steel Pipe Culverts. Vitrified clay 

 pipes or sewer pipes are used extensively for small culverts, 

 and are quite satisfactory when covered with a sufficient 



amount of earth. It 

 is desirable, however, 

 that the ends be pro- 

 tected with wing walls 

 made of masonry. 

 Steel or iron pipes are 

 used to a considerable 

 extent; but owing to 

 the thinness of the 

 metal in most cases, 

 they are regarded as 

 of questionable merit. 

 Cast-iron pipes are 

 regarded as quite 

 satisfactory, but are 

 expensive. 



WOfK OI State 



Fig. 97. Concrete culvert after the plan of 



Highway Commis- 



sions. The majority of states now have a highway com- 

 mission or a highway engineer, whose function is to furnish 

 standard plans and specifications for culverts and bridges. It 

 is advised that these plans and specifications should be used 

 in all cases. Besides representing the most improved design, 

 they enable the work to be let by contract in a highly satis- 

 factory way. All features of the construction will be clearly 

 defined as to quantity and quality in the plans and specifi- 

 cations furnished by these officers. 



