eS eee 
ON THE ROAD PROBLEM. 381 
That this result has been attained in a practical way is manifest from 
the pieces of road crust cut out after they have been under traffic for 
Jong periods, and which I now show you. (Specimens exhibited.) You 
will see, if you care to examine them afterwards, that the stones are 
in their places as they were laid down with their plastic binding, that 
no water has penetrated and that no stones have been picked out or 
forced out by the traffic, and that the stones have been held so that they 
have kept their angularity, and therefore do not tend to come out of the 
road. Experience tends to show that such a road will remain sound, 
and that for even twice the period that is possible in the case of a mud- 
water bound road. That you may see how cohesive such a road is, 
Colonel Crompton has prepared for me these specimens of road, 
showing how they will hang as a solid piece even with a heavy weight 
attached, which of course would be impossible with water-bound 
material: It could not be held up at all, but would fall to pieces in 
the very act of taking it out of the road. (Specimens shown.) 
Roads formed as regards the crust in this way are now common. 
There is reason for thinking, from experiments made, that possibly it 
is unnecessary, and indeed disadvantageous, to use any stones of size— 
even of Macadam’s 14-inch—in making the crust. Experiment is 
tending to show that suitable stone, reduced to very small size, such 
as I show you—(specimen shown)—and properly treated with a binder, 
will produce crust material of a most satisfactory kind. I have here 
numerous briquettes of such a combination of small stone bound with 
suitable material which have proved to be of great strength. 
Tt will be observed, if the specimens are examined, that the cohesion 
is so close that when fracture occurs the stone, in many cases, is 
not pulled out of the structure, but is broken across, its halves remaining 
embedded in the binding material. These briquettes of six square 
inches of surface will resist a pressure applied to the unsupported middle 
of several hundred pounds, while ordinary crust material would break 
on a slight pressure. It is the difference between material that will 
crumble and material that will cling together—between stone set in 
mud and stone bound with a strongly cohering substance. 
One question remains—will it not be well to endeavour to provide 
an elastic skin or carpet to lie between the vehicle and the bearing crust ? 
This question is also engaging attention. Can we find some material 
for the exposed surface of the road which shall be resilient, yielding 
to traffic, but resuming its form and surface? Just as in a golf club 
house we protect our floor from being dug into and worn away by the 
hob-nailed shoes of the golfer by using a thin film of semi-resilient 
covering, such as kamptulicon or ribbed indiarubber, so it is a question 
whether we may not protect our road floor—the road crust—by covering 
it with a film of some substance which will yield and recover without 
disintegrating in the process. The laboratory experiments made seem 
to indicate that this will be accomplished. There are certain materials 
which at ordinary temperatures are, though solid to look at, really in 
a liquid though viscous state. They will flow, but slowly. Their surface 
if pressed down will yield, but in time will resume its level. It is of 
such yiscous pitchy material that the stones of the crust are bound 
