376 REPORTS ON THE STATE OF SCIENCE.—1912. 
labours, to hear the phrase ‘ water binding ’ used to describe the means 
employed for consolidating the crust. To call a water-formed road a 
‘macadamised’ road is a contradiction in terms. His emphatic 
declaration was: ‘ Every road is to be made of broken stones, without 
mixture of earth, clay, chalk, or any other matter that will imbibe 
water.’ 
But further, another disadvantage has shown itself very markedly 
as a result of steam-rolling. The heavy road-roller coming on to a 
layer of stones, surrounded with liquid—and therefore non-resisting— 
mud, and pressing down the stones by its weight, necessarily must 
move the water and-the dirt in suspension, otherwise the stones would 
not go close together. The liquid is therefore squeezed out of the way, 
and as the great width of the roller prevents its escape sideways, except 
at the edges, it must go forwards, and (water being practically incom- 
pressible) the water and the dirt and the stones in front are forced 
upwards, forming a ridge before the roller. (Diagram shown.) It 
advances, and when it cannot force the ridge farther forward, it then 
mounts it and descends in front, and so da capo, with the consequence 
that the road becomes a series of ridges and furrows, and when drying 
up resembles a mackerel’s side, a series of dark-toned wet hollows, and 
light-toned dry mounds. The road becomes bumpy for the traveller, 
and is unable to free its surface from water, and the material remaining 
soft and wet in the furrows, and becoming dry in the ridges, is open 
to destruction by the feet of the horses and the wheels of vehicles 
dumping down and striking compressing blows in the hollows. No 
worse state of matters for the traveller and his vehicle, or for durability 
of the road surface, can be conceived. Yet any observant person must 
have seen this road condition extending for long distances within a very 
short time after the crust has been put down. 
Then let me call attention to another evil which is the consequence 
of rolling wet mud into the interstices of the road. Whenever the 
slightest depression takes place, and water lodges in it, the horse’s hoof 
or the wheel descending into the depression forces out the water and 
with it the dirt binding and throws it on to the surface of the road. It 
is commonly supposed that the potholes which show themselves in 
roads over which heavy traffic passes are caused by an alleged sucking | 
action of the pneumatic tires of the motor vehicle. This is a mistake. 
The proof that there is no appreciable sucking action is shown by the 
fact—which anyone can observe for himself—that where a wheel with 
studs has passed over a stretch of half-dried mud, the impressions of 
the studs are as sharp and as exact in roundness as when they were 
made by the stud descending on to the road. This would be impossible 
if the tire had a sucking action. The marks would then be ragged, and 
there would be loose mud lying on the line of the track. What actually 
happens, when the tire strikes a wet, muddy part of the road, and most 
of all when it strikes down with a blow into puddle depressions, is that 
the water below, being squeezed out sideways, carries with it the soft 
mud in the hole, which is shot out horizontally from the track. I show 
you a diagram of the appearance of the road after the vehicle has dumped 
down into the depression. There is the clean tire mark. Outside it 
