A manual of the principles and practice of road-making: comprising the location, construction, and improvement of roads, (common, macadam, paved, plank, etc.) and rail-roads. By W. M. Gillespie ...

64 WHAT ROADS OUGHT TO BE.
DEDUCTIONS FROM MORIN S EXPERIMENTS.
1. The resistance, or " Traction," is directly propor
tional to the load, and inversely proportional to the diam.
eter of the wheel.
2. Upon a paved, or a hard Macadamized road, the resistance is independent of the width of the tire when it
exceeds from 3 to 4 inches. On compressible roads, the
resistance diminishes when the breadth of the tire increases.
3. At a walking pace, the traction is the same, under
the same circumstances, for carriages with springs, or
without them.
4. Upon hard Macadamized and upon paved roads, the
traction increases with the velocity; the increments of
traction being directly proportional to the increments of
the velocity, above a speed of about 2- miles per hour;
but it is less as the road is more smooth, and the carriage
less rigid, or better hung.
5. Upon soft roads of earth, or sand, or turf, or roads
freshly and thickly gravelled, the traction is independent
of the velocity.
6. Upon a well-made and compact pavement of hewn
stones, the traction at a walking pace is not more than
three-fourths of that upon the best Macadamized road
under similar circumstances: at a trotting pace it is equal
to it.
7. The destruction of the road is in all cases greater as
the diameters of the wheels are less and it is greater in
carriages without than w'th springs.