TRINIDAD AND BERMUDEZ ASPHALTS 



23 



to the evolution of gas at the center, from which point the pitch rolls 

 over toward the edges. This is shown by the fact that pieces of wood 

 which emerge erect at the center are gradually carried to the circum- 

 ference, their deflection from the perpendicular increasing as the dis- 

 tance from the center increases. At the channel they topple over and are 

 again engulfed in the pitch. This illustrates very well the activity of 

 the entire surface of the deposit, although it is much more active near 

 the center of the lake. 



As to the depth of the lake, borings made in 1894 at the center, 

 were carried to a depth of 135 feet, by means of a wash drill, the entire 

 distance being through asphalt of the same character as that at the sur- 

 face. This result shows the great depth of the crater, and the uni- 



Photo, C. R. Toothaker, Phila. Comm 

 Flaking out the Pitch. 



Mai Museum. 



formity of the material which it contains. At the pitch lake, therefore, 

 at a point 138 feet above the sea, there is a bowl-like depression, 

 more than two thousand feet across, and over 135 feet deep, reaching to 

 the sea level, and filled with a uniform mass of asphalt, a mass which 

 must amount to many million of tons, making it the largest deposit of 

 solid native bitumen in the world. 



The material forming this deposit is an emulsion of water, gas, 

 bitumen and mineral matter, the latter consisting largely of fine sand 

 and a lesser amount of clay. It is in constant motion, owing to the evo- 

 lution of gas, and for this reason whenever a hole is dug in the surface, 

 whether deep or shallow, it rapidly fills up, and the surface resumes its 

 original level after a short time. "While sufficiently soft to accommodate 

 itself to any change of level and to slow movement, it can be readily 



