RESULTS WITH THE DTNAMOMETEE. 85 



few inches of mud are sufficient to retard his wagon so 

 much that it wiJl not run of its own weight down a slope 

 of one foot in four (and few common roads are ever 

 steeper), then he may know that a force equal to one-fourth 

 the whole Aveight of his wagon and load will be required 

 to draw it on a level over a similar road that is, the 

 enormous force of five hundred pounds will be needed for 

 one ton, of which many wagons will constitute nearly one- 

 half. Hence he can not fail to see the great importance, 

 for the sake of economy, and humanity to his team, of 

 providing roads, whether public or private, of the hardest 

 and best materials. 



RESULTS WITH THE DYNAMOMETEK. 



Another mode of determining the resistance of roads is 

 by means of the Dynamometer *^ It resembles a spriiig- 

 balance^ and one end is fastened to the wagon and the 

 other end connected with the horses. The force applied 

 is measured on a graduated scale, in the same way that 

 the weight of any substance is measured with the spring- 

 balance. A more particular description of this instrument 

 will be given hereafter. 



Careful experiments have been made with the dynamom- 

 eter to ascertain accurately the resistance of various kinds 

 of roads. The following are some of the results : 



On a new gravel road, a horse will draw eight times as 

 much as the force applied ; that is, if he exerts a force 

 equal to one hundred and twenty-five pounds, he will 

 draw half a ton on such a road, including the weight of 

 the wagon, the road being perfectly level. 



On a common road of sand and gravel, sixteen times as 

 much, or one ton. 



On the best hard-earth road, twenty-five times as much, 

 or one and a half tons. 



* From two Greek words, dunamis, power, and metreo, to measure. 



