296 MASSACHUSETTS AGRICULTURE. 



In economy of repairs, the roads having artificial foundations 

 for the coverings, and otherwise thoroughly constructed, are 

 superior to any others. The saving in the expense of their 

 maintenance will generally in a little time compensate for the 

 excess of original cost. In economy of use they are superior in 

 offering less resistance to draught, thus allowing greater speed to 

 be made and heavier loads to be carried with the same animal 

 power. 



Methods have been contrived for measuring with accuracy the 

 force required to haul loads over different kinds of road surface, 

 or up and down different inclinations at the various ordinary 

 speeds of travel for all sorts of vehicles used. With these many 

 experiments have been made, and the results generalized by 

 means of formulas so as to be applicable to any particular case. 



Some of the results obtained from experiments made by M. 

 Morin at the expense of the French Government, are as fol- 

 lows : — 



1. The traction is directly proportional to the load, and in- 

 versely proportional to the diameter of the wheel. 



2. The width of the tire, if above three inches, does not affect 

 the traction upon paved or hard macadamized roads. 



3. There is no difference of traction for carriages with or 

 without springs going at a walking pace on the same road. 



4. Upon hard macadamized, and upon paved roads, the 

 traction increases with the velocity ; the increase of traction be- 

 ing directly proportional to the increase of velocity if greater 

 than two and one-fourth miles per hour. The increase of trac- 

 tion arising from an increase of speed is less in proportion to the 

 smoothness of the road, and the lightness with which the car- 

 riage is hung. 



5. Upon soft roads of earth, or sand, oi turf, or roads fresh 

 and thickly gravelled, the traction is independent of the velocity. 



6. The traction, at a walking pace upon a well made and 

 compact pavement of hewn stones is not more than three-fourths 

 that on the best macadamized roads. 



7. Carriages without springs are more destructive to roads 

 than those with them, and the less the diameter of the wheels 

 the more destructive they are. 



Sir John Macneill, with an instrument for measuring forces 

 required to haul loads over different surfaces, obtained, from 



