462 OUR COMMON ROADS—MURPHY. 
zontal line will be equal to the force necessary to draw the load 
and the load itself upon the same road when level.—Gilmore, pp. 
24,25. (Experiments from Morin, and Sir J. McNeil.) 
In practice the steepest grades on good roads is about 1 in 20, 
it having been determined by experience that a horse can draw 
up this incline his ordinary load for a level road without the 
help of a second animal; also that he can attain at a walk, a given 
height, upon a gradient of 1 in 20 without more apparent fatigue, 
and in nearly the same time as he would require to reach the 
same height over a proportionally longer slope so gentle—say ;,— 
that he could ascend it at a trot. 
WHEELS AND WEIGHTS ON THEM. 
The regulation of the form of construction of wheels has been 
the subject of legislation in Great Britain since the beginning of 
the century. One of the results was to bring into use an exces- 
sively broad conical wheel with a tire considerably rounded. 
The conical or dished wheel had its advocates and its enemies. 
The width of the wheel and the weight carried on them have an 
important influence on the wear of roads. The restrictions at 
present in force in England are those of the General Turnpike 
Act (3 Geo. IV. cap. 126), which regulates the weights to be 
allowed to wagons, carts, &c., in winter and in summer according 
to the following table: 
Weight of Carriage and Pressure per wees Width 
DESCRIPTION OF VEHICLES. ae 
Suinmer. Winter, Summer, Winter. 
Waggon with 9 in. wheels 6 10/6 0 3.6 3.3 
Cart 7 m rel Ola tebe a 3.9 3.0 
Waggon, 6 in. wheels..... Ai | Aw 5 4.0 3.5 
Cart Ride ey Mier Soe Se OO AUS 5.0 | 4.6 
Waggon with 44 in. wheels, 4 5 | 3 15 14.7 4.1 
Cart " Dio MD eal a ey, ‘5.8 5.2 
Waggon with less than 43 , 
TM WNCEIS si 5.s eee re oD} Bia eed : 7.5 6.5 
Cart with less shan 44 in. i OLS 
wheels: ed. 00%, 1°45) 2.10 (oR he vee 
