Foundations ; Drainage ; Materials. 
33 
The vehicles which try the foundations of roads most 
severely are traction engines, and the law regarding them is in 
much need of revision. In the opinion of Mr. Maybury, the 
County Surveyor of Kent, where 170 traction engines are 
regularly at work, there is now no economic necessity for 
such appliances, owing to the advent of the heavy motor ; and 
it is to be hoped that, if traffic with traction engines is to be 
continued, they will ere long be improved by the application 
of the “ Pedrail,” or otherwise, in order to reduce the damage 
they now cause by tearing up the road surface and deforming 
or breaking through the road crust. A traction engine con- 
centrates weight and forces tangential to the road surface to 
a much greater extent than any other vehicle. 
Drainage. 
The drainage of the subsoil and surface of roads, though 
a matter of the very greatest importance, seldom receives 
sufficient attention and is rendered difficult in Great Britain 
because a sufficient width has seldom been secured or retained 
for the roads. On many miles of our highways the cost of 
special piped drains laid under the centre of the road for 
subsoil and surface drainage would be amply repaid by a 
decrease in the cost of maintenance. Open drains are out of 
the question in most cases and should not be tolerated on 
the road sides except where separated from the travelling 
way by a fence or wide sodded margin. When closed 
drains are used, the outlets for surface water should be of 
a simple, safe, and strong design, with detritus pits and 
hinged gratings. 
According to evidence given by Sir John Macneil in 1831 
before the Select Committee on Steam Carriages, the wear on a 
portion of a road on a wet clay bottom was found, by accurate 
experiment, to be eight times as much as the wear on another 
portion of the same road with a solid dry foundation. 
Quality and Size of Materials. 
For the lower layers in road construction any moderately 
hard stones may be used, but for the upper layers which form 
the working surface it is true economy to take every pains 
to obtain materials which are hard, tough, and impervious. 
The best materials are certain kinds of granite (many 
granites are too soft for macadam), syenite, diorite, and basalt. 
For the upper crust of roads the stones should be broken to 
pass in any direction through a ring not exceeding two and 
a half inches in diameter. In Mr. Wheeler’s paper already 
referred to, particulars are set out of the great saving made 
in the maintenance of roads by the use of granite, costing 
13s. 6d. per ton, instead of local materials costing less than 
VOL. 67. D 
