ASPIIALTUM FOR A MODERN STREET. 



235 



Railroad, are very extensive deposits of coquina or shell limestone, filled 

 with bitumen. As found, the material is very tough and difficult to 

 break. When the bitumen is dissolved out with chloroform, there re- 

 mains a mass of small shells, very light and porous, but with sufficient 

 stability to form a rock. The shells contain from nine to thirteen per 

 cent, of bitumen. While a large sum has been expended on a plant 

 for extracting this bitumen, the enterprise has never proved a pecuniary 

 success. In northern Texas, near the Eed Eiver, are extensive deposits 

 of bituminous sand, which has been used locally for sidewalks with suc- 

 cess. Across the Eed Eiver, near the Arbuckle Mountains, in the 

 Chickasaw Nation, beds of bituminous sand occur of great extent. They 

 extend across the country in anticlinal folds for miles in length. The 

 material is not stone, as the sand falls into a powder as soon as the 



Fig. 7. The ' Big Spring ' of Tar. 30 Feet in Diameter. Upper O.tai. Ventura County, Cal 



bitumen is removed from it. When the material is broken into small 

 pieces and placed in boiling water, the bitumen rises to the surface 

 nearly free from sand, while the bulk of the sand sinks through the 

 water clean. The bitumen thus obtained is of very superior quality for 

 any purpose. Still farther north and east, near the town of Dougherty, 

 several deposits occur. One is a mass of great extent of fragments of 

 chert and limestone cemented together with bitumen. A mastic has 

 been made by grinding this material. Another mass consists of a magne- 

 sian chalk, of carboniferous age, saturated with bitumen. Another is a 

 mass of large shells filled with more than twenty per cent, of bitumen. 

 Other deposits of loose sand occur in beds, saturated with ten per cent, 

 of bitumen. These materials have been used separately and ground 

 together for paving mixtures for street surfaces. 



