CHAPTER XXIII 
MINERAL OIL? 
PetroLEUM — HisTorY AND NATURE — Petroleum is the 
second in importance of mineral fuels. The name is medi®val, 
and means rock oil, for, as remarked in 1543 petroleum 
** droppeth out of rocks.” Many places, such as Pitchford 
in Derbyshire, and Pechelbronn (i.e. Pitchspring) in Alsace, 
are named after oil springs. Petroleum, however, dropped 
out of the rocks in North-western Europe in such small 
quantities that it was only used as medicine or cart grease. 
In other countries it was used in early times, as by the 
Peruvians for embalming mummies, by Noah to caulk his 
ark, and as the mortar for the Tower of Babel. Later in 
the Bible it is mentioned as used in paving, for the parable 
of the salt that has lost its savour, and is fit only to be cast 
out and trodden under the foot of man, probably refers to 
petroleum which has lost its volatile constituents, and is 
useful for road making. Crude petroleum is usually a dark 
brown to greenish-brown fluid, though it occasionally under- 
goes natural filtration and is almost water-clear as in some 
Canadian and Trinidad wells. It is a hydrocarbon of ex- 
tremely varied composition. In the methane or paraffin 
series each molecule of carbon is combined with the maximum 
quantity of four molecules of hydrogen, so that the carbon 
is fully saturated. The paraffin series is represented by the 
formula CoHyy 45, e.g. CH, Other groups are marked by 
lesser proportions of hydrogen, so that the compounds are 
usually unsaturated. The chief series are the ethylene or 
olefine, CyHyy (e.g. CoH) ; acetylene, CoH 5 (e.g. C,H); 
! The U.S. gallon holds 8-33 1b. of water, the Imperial gallon holds 
10 lb. ; the barrel contains 42 U.S. gallons and 35 Imperial gallons; the 
metric ton is 6-295 barrels, 2204 Ib. or 1000 kilograms. 
275