WHINERY'S METHOD. The foundation may be either broken stone or hydraulic cement concrete, depending upon the relative cost of the two and also upon the supporting power of the subsoil. The wearing coat consists of a layer of crushed stone the voids of which are filled with a mixture similar to that used for the wearing coat of sheet asphalt pavements. Broken stone of properly graded sizes is spread on the foundation to the requisite thickness, which, either before or after it is thus spread, is heated to a tem perature of about 300° F. A hot mixture of asphaltic cement and • mineral grains is spread over the top of the layer of hot crushed stone in a sufficient quantity to fill the voids in the stone and to level up the tinevenness of the surface, the layer being properly graded with paving rakes. When this operation is completed a steam roller of the asphalt type weighing not less than ten tons is to be operated over the surface until (1) the plastic composition is forced into the voids in the crushed stone, (2) the unevenness of the surface is filled up, and (3) the whole mass is thoroughly compressed and solidified. The roadway is then complete, and after giving it time
to become cold and hard the street is opened to travel.
No pavement of this kind has been constructed , but the in ventor, an engineer of large experience in laying asphalt pavements, claims that it will have the following advantages over ordinary sheet asphalt pavements. 1. The first cost will be materially less. 2. It will offer a better foothold to horses. 3. It will be at least as durable as the ordinary sheet pavement. 4. It will not shift under travel and work into waves. 5. It will not crack. 6. It can be repaired more cheaply and with less skilled labor than can the ordinary sheet pavement. On the other hand the asphalt macadam will not be s..) smooth and probably not so noiseless as the ordinary asphalt pavement.