202 ENGINEERING ON THE FARM 



shape with the road drag. Other materials used in road 

 construction, some to a very limited extent and others widely, 

 are as follows: a mixture of sand and clay, burnt clay where 

 fuel is plentiful, shells along the coast, gravel and coarse 

 sand as found in natural banks, broken stone of the more 

 common geological rocks, wood in the form of planks for 

 clay roads and as sawdust, bark or straw for sand roads, 

 oil, asphalt, and tar as a binder on sand, gravel, and 

 broken rock, bituminous concrete, asphalt, paving brick, and 

 cement concrete. Such materials have proved satisfactory in 

 many localities, but it should be understood that the method 

 of treating a road with some of these in one locality may 

 not be satisfactory in another, and that there is need for 

 careful experimental work with road-surfacing materials in 

 new localities. 



Construction. There are certain underlying principles 

 involved in the construction of roads regardless of the nature 

 of the covering. In agricultural communities the location 

 of the road is usually determined by the land lines, there 

 being a strong sentiment against securing better grades by 

 locating the roads around hills rather than over them. 

 The location of the road on a section line frequently involves 

 a heavy cut and fill and also the use of steeper grades than 

 might be necessary if more latitude were allowed in the 

 location. In localities where more choice of location is 

 permitted, better roads can be secured for less money by 

 the expenditure of some time and the exercise of judgment 

 in making the location, as is done in the case of railroads. 

 The question frequently arises between the relative desir- 

 ability of having a rise and fall or increasing the length of 

 the road. It has been demonstrated that it takes approxi- 

 mately the same power to raise a load through one foot 

 vertically as to haul it 20 to 30 feet horizontally along an 

 ordinary dirt or gravel road. Therefore, to eliminate a 

 foot of rise, the length of the road may be increased 20 to 30 

 feet. It must be remembered, however, that the increased 



