44 FLORIDA GEOLOGICAL SURVEY—I4TH ANNUAL REPORT 
the actual specific gravity expressed in the ordinary way is less than one. 
However, in ordinary usage a special scale has been devised known as 
the Baume scale, in which the gravity is expressed as whole numbers. 
On the Baume scale distilled water at 60° F. has a gravity marked as 10°, 
and the figures on this scale are so arranged that they increase as the 
gravity of the fluid decreases. Thus a heavy oil, but little lighter than 
water, may read 12° to 15° B., while a lighter oil may be found to read, 
say, 35° to 40° B. The gravity changes somewhat with temperature, 
and in practice the gravity is commonly given as at 60° F. If taken at a 
temperature other than 60° F., it may be reduced to the 60° equivalent. 
Paraffin base oils are usually light, and hence on the Baume scale have 
a higher reading than asphalt base oils. The color of crude oils varies 
from light yellow, or straw color, to black. As a rule, oils of light color 
are likewise light in gravity. The odor varies decidedly, depending 
probably upon included gases. Hydrogen sulphide gas is often present 
in oils from limestones, giving a disagreeable odor. A terpine odor 
is occasionally detected, chiefly on light colored oils. Aromatic odors 
and an odor of gasoline characterize some of the crude oils. 
Another property in which oils differ much among themselves is 
viscosity, or fluidity. As a rule, the light, or paraffin base oils, flow 
readily. Some of the heavy oils are so viscous as to require heating 
somewhat before they can be pumped through a pipe line. 
THE ORIGIN OF PETROLEUM 
The probable origin of petroleum in the earth has given rise to much 
discussion. It has been found by laboratory experiments that hydrocar¬ 
bons may be obtained from organic substances and likewise from cer¬ 
tain of the inorganic substances. From, fish oil, hydrocarbons which 
are similar to those obtained from the petroleums have been obtained 
by destructive distillation. Wood and vegetable oils have likewise been 
shown to yield hydrocarbons. From cast iron, spiegeleisen and ferro¬ 
manganese, when dissolved in a mineral acid, such as hydrochloric, there 
is evolved hydrogen and smaller quantities of hydrocarbons. 1 The 
hydrocarbons in these experiments are probably to be ascribed to the 
carbides contained in the iron. It is a matter of common knowledge also 
that most carbides react with water and form hydrocarbons. 
1 A Treatise on Petroleum. Sir Boverton Redwood. Vol. I, Sec. 4, 1913. 
