. The Popular science monthly . , 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 itsoriginal level after a short time. While sufficiently soft to accommodateitself to any change of level and to slow movement, it can be readily 24 THE POPULAR SCIENCE MONTHLY flaked out with picks, in large conchoidal masses weighing from 50 to75 pounds. It is honeycombed with gas cavities, and resembles inappearance the structure of a Swiss cheese. The gas evolved by thepitch consists of hydrogen sul
. The Popular science monthly . , 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 itsoriginal level after a short time. While sufficiently soft to accommodateitself to any change of level and to slow movement, it can be readily 24 THE POPULAR SCIENCE MONTHLY flaked out with picks, in large conchoidal masses weighing from 50 to75 pounds. It is honeycombed with gas cavities, and resembles inappearance the structure of a Swiss cheese. The gas evolved by thepitch consists of hydrogen sulphide and carbon dioxide, but in such pro-portions that it burns readily when a match is applied, although theflame is not maintained for any length of time. In the center of the so-called lake is a point where there is a con-tinued influx of soft material, accompanied by a stronger evolution ofgas, which gradually hardens and becomes like the remainder of thedeposit. The point of evolution of the soft material moves about from. Photo, W. H. Rau, the Crude Pitch, Refinery in Distance. place to place along lines of least resistance. As that evolved at onepoint hardens the fresh material breaks out elsewhere. It is peculiarin that it is associated with so much free water which rises with it, thatit can be handled freely and made into a ball without adhering to thehands. It is in an active state of change, since if it is sealed in a tincan the gas evolved will, in a few weeks, burst the containing vessel. The temperature of the pitch at the surface is no greater than thatof the surrounding air except when it is exposed to the noon-day sun,when it may rise to 130° F. or over. That of the soft pitch is no higherthan any other pait of the deposit. TRINIDAD AND BERMUDEZ ASPHALTS 25
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