Page:Popular Science Monthly Volume 58.djvu/234

226 attracted attention. There were veins of material in Cuba that were also included in the argument, Coal vs. Asphalt.

The late Dr. T. Sterry Hunt, as long ago as 1863, separated asphaltuni from pyrobituminous minerals, or minerals that on being heated to destructive distillation yield products that resemble bitumens. These pyrobituminous coals, schists and shales are nearly as insoluble in the solvents of bitumen, viz., ethyl ether, chloroform, benzole, etc., as they are in distilled water; hence, Dr. Hunt made the action of these solvents the test of the two classes of substances. All true bitumens are miscible with or almost wholly soluble in chloroform, a test that clearly separates them from pyrobituminous minerals. So-called 'asphaltic coals' are not coals at all, but are geologically old asphaltums.

Besides the asphaltums, almost wholly soluble in chloroform, there are a large number of minerals that consist only in part of true bitumens. These are found as beds of sedimentary or crystalline rock, often of immense extent and thickness, impregnated with bitumens of varyi inconsistency and quality, sometimes very soft and seldom quite solid after being separated from the rock. In some instances the bitumen appears to be convertible into asphaltum, and in others not. The French writers have called these rocks 'asphalte,' but, unfortunately, they have also called asphaltum by the same name, as if the things w r ere identical and the words synonymous. Among English writers no uniform custom prevails, but German authors use generally the French word, at the same time calling asphaltum 'Erdpech' or 'Glanzpech.' I think it would promote clearness of expression if this word 'asphalte' were uniformly introduced into all modern languages to designate those bituminous rocks, with the qualifying words, siliceous, calcareous or argillaceous, added as required.

The so-called Trinidad pitch, as it is found in and around the lake, on the island of Trinidad, is a mixture of bitumen, water, mineral and vegetable matter, the whole inflated with gas. When removed from the deposit, most of the water dries out, the gas escapes, the mass changes in color from brown to blue-black, becoming brittle, and at the same time more or less sticky as it loses water. At a rough estimate, about 25 per cent, of the natural cheese-pitch is bitumen.

Various theories have been formulated by scientific men to' account for the origin of asphaltum and other forms of bitumen. By some it is thought that complex chemical changes take place between water. •carbonate of lime and iron, and other elements that are supposed to exist in the free state or in combination with carbon as carbides, at great depths from the surface. When they have been formed they are supposed to rise towards the surface with steam and water. This is called the 'chemical' theory. Others think that organic animal and vegetable matter that has been buried in strata near the surface of the