436 OUR COMMON ROADS—MURPHY. 
Telford held that when the bottom is soft and wet, and the 
sub-soil cannot be properly drained, a bottoming of some sort 
was desirable, and where stone can be easily got for a pitched 
foundation, it will be found a most economical as well as most 
convenient way of making a road if it is required to be of con- 
siderable strength. 
McAdam considered a bottoming of large stones useless, and 
even went so far as to condemn it as mischievous, on the ground 
that the large stone at the bottom caused motion of the materials 
and kept open passages for water to the sub-soil beneath. He 
contended that the thickness of the road should only be regulated 
by the quantity of materials necessary to form a stable and im- 
pervious covering, and never with any reference to its power of 
carrying weight, and that if water passed through a road it 
would go to pieces whatever was its thickness. (Remarks on 
Road-making, by J. L. McAdam, p. 40.) 
- McAdam’s doctrines are generally condemned as contrary to 
the first principles of science. (Parnell’s Treatise on Roads, p. 78.) 
He also said that he preferred a soft substratum to a hard one, 
provided it were “not such a bog as would not allow a man to 
walk over it.” (Evidence of Select Committee on Highways, 
1819, p. 23.) 
To McAdam, nevertheless, is due the credit of having been the 
first to introduce the proper method of breaking and preparing 
road materials, and to the possibility of forming them into a com- 
pact road surface. To him also is due the establishment of a 
regular system of road maintenance under properly qualified 
surveyors. | 
Various forms and modifications of McAdam’s and Telford’s 
systems have been since adopted with varying success. Mr.Baylis, . 
in his suburban practice (see Fig 3), laid a 3-inch coat of 2-inch 
cubes, which were allowed to become consolidated by the traffic, 
when he spread a second coat of the same thickness, and covered 
it with a thin gravel blinding. Others have tried slag or hard 
foundry refuse from 6 to 8 inches in depth, and the result justifies 
its continuance in certain localities. Mr. Joseph Mitchell, of 
Inverness, has introduced in the summer of 1865, one of the best 
