COMMON ELEMENTS OF THE EARTH 151 



Some of the beds beneath the coal contained remains of 

 marine life. Decay caused gases rich in carbon to be forced 

 into the crevices of the rocks, where some of these gases 

 \\ere condensed into liquid petroleum. When borings are 

 made through the rocks near certain coal regions, petroleum 

 or a gas comes from the openings, sometimes for years with- 

 out cessation. The products from distillation of petroleum 

 are very numerous. Among those most widely used are 

 kerosene, gasolene, vaseline, and paraffin. Natural gas is 

 used for fuel as well as for light in many parts of the United 

 States. 



Charcoal is prepared by heating wood in a kiln or oven, 

 where air cannot enter. Gases and steam are driven off, 

 and carbon in a solid, nearly pure form is left. The process 

 is similar to the method by which coal was made under 

 the rocks during many centuries, but is very much more 

 rapid. 



Carbon occurs in many compounds in the bodies of plants 

 and animals. It is the union of this carbon with oxygen 

 (slow combustion) which furnishes the energy needed to keep 

 the body alive. All kinds of grains and fats furnish carbon 

 compounds in large quantities and nitrogen compounds in 

 small quantities. (LABORATORY MANUAL, Exercise XVII.) 



165. Phosphorus and Sulphur. The two solids, phos- 

 phorus and sulphur, are often associated in the minds of 

 people because both are readily combustible and have low 

 kindling points, and because they have been used together 

 for a long time in making the tips of matches. Phosphorus 

 occurs naturally only in compounds. The element is pre- 

 pared artificially from the hard part of bones, which is cal- 

 cium phosphate. Phosphorus is a wax-like, slightly yellow 

 substance which has the property of being self-luminous, 

 that is, it gives off a faint light. On account of its rapid 

 union with oxygen if exposed to air, it is kept under water 

 in laboratories and factories. 



