452 OUR COMMON ROADS—MURPHY. 
treated. The gravel, if at all mixed with earthy material, should 
be screened ; it should be spread to a depth of from 4 to 6 inches, 
or to such depth and width as may be considered necessary 
according to the volume of traffic to run over it, blinded with 
fine material and rolled. 
If the bed of the road is rock, a layer of earth is frequently 
interposed between it and the gravel to prevent the too rapid wear 
of the latter, and assist in forming the crust. Where the road has 
already attained the desirable shape or form, and where the 
drainage is yood, different treatment may be necessary for 
economy, and in many cases more judicious, especially for traffic 
not very heavy. 
The relative strenoth and durability of different road material 
is a difficult matter to determine. No test but actual wear on 
the road can be fully relied on, and though it is easy to see that 
some pebbles or stones wear three or four times as long as others, 
it is almost impossible to take into account all the circumstances 
under which they are exposed to wear. The nature of the traffic, 
the moisture or dryness of the crust, and susceptibility to disin- 
tecrate from freezing and thawing, has often a great effect on 
the wear of the same material. It is only by studying such 
effects and by practical application we can find the most suitable 
materials and discover the best methods to employ them, for their 
necessary treatment and behaviour, may vary as the nature of 
surface and the conditions under which they are placed, may vary. 
PLANK ROADS. 
Eight years ago a planked road was laid over a swamp or bog 
near Liverpool, Queens County, on the leading highway from 
Milton to Caledonia, with some degree of success. It is claimed 
by the members representing the County of Queens that the 
result justifies the practice, and that in certain situations their 
adoption might be judiciously extended. The planks were laid on 
sleepers or stringers, in the same manner as General Gilmore 
describes the method generaily used in the United states, and it 
is claimed that they answered their purpose admirably, and that 
the roadway over them is in good condition to-day. The writer 
