2 
BULLETIN 102, UNITED STATES NATIONAL MUSEUM. 
1. THE RESOURCE. 
NATURE. 
Petroleum, or crude petroleum as the raw or unrefined product is 
often termed, is an oily liquid varying considerably in appearance 
according to the locality from which it comes. It is an extremely 
complex mixture of organic compounds, chiefly hydrocarbons , 1 but 
substances containing sulphur, oxygen, and nitrogen are also present 
in small amounts. It contains, therefore, five chemical elements of 
the first importance in life processes, a circumstance that suggests 
at once an organic origin and determines the important role that 
this substance is due to play in filling the needs of man . 2 
If crude petroleum is exposed to the air, it gradually thickens until 
a solid residue is left. The first product given off is natural gas; 
then liquid components evaporate in the order of their lightness ; and 
the final residue is composed largely of either paraffin wax or as- 
phalt. Petroleum is thus seen to be a mixture of different liquids 
dissolved in one another and holding in solution also natural gas and 
solid substances. This conception correlates natural gas as a by- 
product of petroleum 3 and affords a simple epitome of the changes 
more rapidly induced when petroleum is subjected to refining . 4 The 
asphalt lake of Trinidad and the ozokerite deposits of Galicia and 
Utah represent natural residues from the proloqged evaporation or 
natural distillation of petroleum. 
While petroleums vary considerably in character, they fall chiefly 
into two classes according to whether the residue yielded is pre- 
dominantly paraffin wax or asphalt . 5 This broad distinction is of 
great economic significance, because the paraffin petroleums, occur- 
ring chiefly in the eastern part of the country, came first into use 
and therefore determined the current refining practice and the exist- 
ing demand for petroleum products; while the asphaltic petroleums, 
exploited later in the Gulf region and California, found their imme- 
diate commercial outlet in the form of fuel. The higher gasoline 
content of paraffin oils, coupled with the distance of coal from the 
Californian region , 6 gave free scope to the economic differentiation 
of the two types. 
1 Compounds composed of hydrogen and carbon. These substances are present by the 
hundreds. 
2 It would be shortsighted to assume that petroleum even now has displayed its full 
measure of versatility. 
3 Part of the natural gas production of the country, indeed, comes from petroleum 
wells. 
4 The processes of refining, of course, involve some chemical changes also. 
B The first are said to have a paraffin base; the second, an asphaltic base , or called 
merely asphaltic petroleums. There are also intermediate oils with almost equal pro- 
portions of paraffin and asphalt. 
6 The presence of coal fields in California, however, would have scarcely deterred the 
development of the oil fields of that State, although their presence would afford a pleas- 
ing contemplation now. 
