THIRD ANNUAL YEAR BOOK — PART I. 29 



decrease the cost of culverts. For instance, a 24-inch culvert pipe with 

 a fall of only 1 inch in 100 feet has a capacity of about 2,300 gallons 

 per minute, while a pipe of only half that size, when given a fall of 3 

 feet to the 100, has a capacity of about 2,500 gallons per minute. Fall is 

 therefore a very important factor in disposing of water. 



CONCRETE DRAINS AND CULVERTS. 



Culvert or bridge construction forms a very important branch of 

 highway improvement. Large sums are often appropriated for this 

 actual improvement of the road. It would be impossible, in the space 

 allowed here, to include many details in reference to bridge work, but 

 it is so very important that it can not be passed by without comment. 



Wooden bridges and culverts wear, warp and decay so rapidly under 

 the action of rain, sunshine, frost and traffic that their usefulness is very 

 short, and their maintenance consequently very expensive. Wherever 

 the expenditure will justify, and the materials can be had, it is much 

 more economical in the long run to use sewer pipe, home made or manu- 

 factured concrete pipe, or stone, brick or concrete arches to carry the 

 water under the road. These materials are much more durable than tim- 

 ber, and if protected from frost and traffic they can be considered per- 

 manent. 



Molds for making concrete pipe can be constructed of spring steel and 

 can be secured at a foundry for a few dollars. They are composed of 

 an inner and outer casing resumbling a stovepipe, and should be about 

 2V 2 feet in length, the inner one being less in diameter, so as to leave 

 a space between the two of from 3 to 5 inches. The diameter of the 

 pipe may be regulated as necessity may require. These molds are set on 

 end on a solid base, with the smaller mold inside. The concrete is then 

 mixed, having a proportion of about one part Portland cement to five 

 parts of clean gravel, and while one person shovels it into the mold an- 

 other rams it down with an iron rammer until the casing is full. The 

 clamps are then loosened and the pipe left to dry, after which it can be 

 placed in position. 



The construction of concrete, brick and stone arches is equally sim- 

 ple. A false work of common boards can be erected in the shape of the 

 arch desired, a perfect semicircle being preferred. If concrete is to be 

 used this arch should be constructed of smooth-planed boards closely 

 boarded up against the work as it progresses. The concrete can then be 

 mixed in the proper proportions and rammed well into position until 

 moisture appears on the surface. The false work for concrete arches 

 should be substantial and should be left in position for ten days or two 

 weeks. Enough earth should be placed on the top of concrete arches, 

 culverts and drains to protect them from the wheels of vehicles. 



SUBDRAINAGE. 



WET LANDS. — Where a road runs through low, wet lands, or over 

 retentive or clayey soils, surface drainage is not all that is required. In 



