298 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
"bitumen " has in the main been used to include the three varieties of 
hydrocarbon compounds known as petroleum, maltha or mineral tar, 
and the solid substances included under the asphaltites and often 
designated, one or another of them, ' ' asphalt. " The adjective ' ' bitu- 
minous," however, may be applied to a sandstone or other rock 
impregnated with bitumen, as thus understood; and if such bitumen 
has any of the characteristics of the so-called asphalts, the compound 
may receive the name "asphaltic sandstone," "asphaltic limestone," 
etc. 
GENERAL FEATURES OF THE HYDROCARBONS. 
The relations, chemical or other, between the hydrocarbons of the 
table on pages 297-298, were they worked out, would doubtless show the 
utmost complexity, for complexity exists even in the substances them- 
selves, nearly all of which are separable by the action of solvents or 
by fractional distillation into two or more components that are in turn 
divisible into series of hydrocarbons, in many instances of great 
extent. 
In Dana hatchet t ite and ozocerite are found among the simple hydro- 
carbons as members of the paraffin series C„Il2„+2, while fichtelite, 
hartite, and a number of others occur in this division of the hydro- 
carbons, but of series other than the paraffin, and in many instances 
altogether of doubtful reference. 
The resinous compounds belong to the class of oxygenated hydro- 
carbons, the membership in which is very extended and of great 
variety. Concerning this class, Dana remarks that it embraces 
"chiefly the numerous kinds of native fossil resins, many of which are 
included under the generic term 'amber;' also other more or less 
closely related substances. In general, in these compounds, weak 
acids (succinic acid, formic acid, butyric acid, cinnamic acid, etc.), or 
acid anhydrides, are prominent." 
Between the coals — especially the bituminous and cannel varieties — 
and the resinous and asphaltite divisions of this table relations are 
readily found ; indeed, for a number of years, only two or three decades 
ago, grahamite, on account of its composition, was regarded by men 
high in authority as a true coal, notwithstanding its wholly different 
mode of occurrence. 
Albertite, grahamite, uintaite, etc., are now accepted as closely 
related varieties of asphaltum. This relationship is evident both in 
their chemical composition and in their mode of occurrence, yet they 
are readily distinguished by their behavior toward solvents, by the 
action of heat upon them — their fusibility, so called — and by other 
properties. 
Wurtzilite, in outward appearance, bears a striking resemblance to 
the asphaltites, but is distinguished from them by its behavior toward 
solvents and by its marked sectile and elastic properties. Yet, while 
