Steep hillsides are paved with cobblestones instead of asphalt.
In this way, the asphalt is held in position, and is an absolute prevention of dampness.
As for where this asphalt come from, I don't know, and nobody knows.
A recent rain had made the clay as slippery as asphalt in a drizzle.
A mixture of sand and asphalt will creep on slopes of 1½ to 1, but asphalt concrete will not.
With asphalt at $20 a ton, and labor at $2 a day, the cost was 15 cts.
The asphalt should be heated in a kettle to a temperature not exceeding 450° F.
Above this two layers of asphalt of an aggregate thickness of ¾ in.
The rest was flat-buildings and asphalt and motor-puddled air.
Coal has essential features in common with asphalt, oil, and gas.