226 POPULAR SCIENCE MONTHLY. 



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 asphal- 

 tuni 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 bitu- 

 mens. These are found as beds of sedimentary or crystalline rock, often 

 of immense extent and thickness, impregnated with bitumens of varyi in- 

 consistency 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 esti- 

 mate, 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 lias been buried in strata near the surface of the 



