It is undeniable that in this country, at least, we are accustomed to
regard coal as the chief, and, indeed, the only substance which falls
to be considered under the name of fuel. In other countries, however,
the case is different. Various materials, ranging from wood to oil,
come within the category of material for the production of heat. The
question of fuel, it may be remarked, has a social, an antiquarian,
and a chemical interest. In the first place, the inquiry whether or
not our supplies of coal will hold out for say the next hundred
thousand years, or for a much more limited period only, has been very
often discussed by sociologists and by geological authorities.
Again, it is clear that as man advances in the practice of civilized
arts, his dependence upon fuel becomes of more and more intimate
character. He not merely demands fire wherewith to cook his food, and
to raise his own temperature or that of his dwelling, but requires
fuel for the thousand and one manufacturing operations in which he is
perpetually engaged. It is obvious that without fuel civilized life
would practically come to an end. We cannot take the shortest journey
by rail or steamboat without a tacit dependence upon a fuel supply;
and the failure of this supply would therefore mean and imply the
extinction of all the comforts and conveniences on which we are
accustomed to rely as aids to easy living in these latter days. Again,
socially regarded, man is the only animal that practices the
fire-making habit. Even the highest apes, who will sit round the fire
which a traveler has just left, and enjoy the heat, do not appear to
have developed any sense or idea of keeping up the fire by casting
fresh fuel upon it. It seems fairly certain, then, that we may define
man as being a "fuel-employing animal," and in so doing be within the
bounds of certitude. He may be, and often is, approached by other
animals in respect of many of his arts and practices. Birds weave nest
materials, ants make--and maul--slaves, beavers build dams, and other
animals show the germs and beginnings of human contrivances for aiding
the processes of life, but as yet no animal save man lights and
maintains a fire. That the fire-making habit must have dawned very
early in human history appears to be proved by the finding of ashes
and other evidences of the presence of fire among the remains and
traces of primitive man.
All we know, also, concerning the history of savage tribes teaches us
that humanity is skillful, even in very rude stages of its progress,
in the making of fire. The contrivances for obtaining fire are many
and curious in savage life, while, once attained, this art seems to
have not only formed a constant accompaniment but probably also a
determining cause in the evolution of civilization. Wood, the fat of
animals, and even the oils expressed from plants, probably all became
known to man as convenient sources of fuel in prehistoric times. From
the incineration of wood to the use of peat and coal would prove an
easy stage in the advance toward present day practices, and with the
attainment of coal as a fuel the first great era in man's fire-making
habits may be said to end.
Beyond the coal stage, however, lies the more or less distinctively
modern one of the utilization of gas and oil for fuel. The existence
of great natural centers, or underground stores, of gas and oil is
probably no new fact. We read in the histories of classic chroniclers
of the blazing gases which were wont to issue from the earth, and to
inspire feelings of superstitious awe in the minds of beholders. Only
within a few years, however, have geologists been able to tell us much
or anything regarding these reservoirs of natural fuel which have
become famous in America and in the Russian province of Baku.
For example, it is now known that three products--gas, oil, and salt
or brine--lie within natural receptacles formed by the rock strata in
the order of their weight. This law, as has well been said, forms the
foundation of all successful boring experiments, and the search for
natural fuel, therefore, becomes as easy and as reliable a duty as
that for artesian water or for coal. The great oil fever of the West
was attended at first, as Professor M'Gee tells us, with much waste of
the product. Wells were sunk everywhere, and the oil overflowed the
land, tainting the rivers, poisoning the air, and often driving out
the prospectors from the field of discovery. In Baku accidents and
catastrophes have, similarly, been of frequent occurrence. We read of
petroleum flowing from the ground in jets 200 feet high, and as thick
as a man's body; we learn how it swept away the huge cranes and other
machinery, and how, as it flowed away from the orifices, its course
was marked by the formation of rivers of oil many miles in length.
In America the pressure of rock gas has burst open stills weighing
over a ton, and has rushed through huge iron tanks and split open the
pipes wherewith it was sought to control its progress. The roar of
this great stream of natural gas was heard for miles around as it
escaped from the outlet, and when it was ignited the pillar of flame
illumined the surrounding country over a radius extending in some
cases to forty miles. It is clear that man having tapped the earth's
stores of natural fuel, stood in danger of having unloosed a monster
whose power he seemed unable to control. Yet, as the sequel will show,
science has been able to tackle with success the problems of mastering
the force and of utilizing the energy which are thus locked up within
the crust of the globe.
As regards the chemistry of rock gas, we may remark in the first place
that this natural product ranks usually as light carbureted hydrogen
gas. In this respect it is not unlike the marsh gas with which
everyone is familiar, which is found bubbling up from swamps and
morasses, and which constitutes the "will o' the wisp" of romance. In
rock gas, marsh gas itself is actually found in the proportion of
about 93 per cent. The composition of marsh gas is very simple. It
consists of the two elements carbon and hydrogen united in certain
proportions, indicated chemically by the symbol CH4. We find, in fact,
that rock gas possesses a close relationship, chemically speaking,
with many familiar carbon compounds, and of these latter, petroleum
itself, asphaltum, coal, jet, graphite or plumbago, and even the
diamond itself--which is only crystallized carbon after all--are
excellent examples.
The differences between these substances really consist in the degree
of fixing of the carbon or solid portion of the product, as it were,
which exists. Thus in coal and jet the carbon is of stable character,
such as we might expect to result from the slow decomposition of
vegetable matter, and the products of this action are not volatile or
liable to be suddenly dissociated or broken up. On the other hand,
when we deal with the _hydrocarbons_ as they are called, in the shape
of rock gas, naphtha, petroleum, tar, asphaltum, and similar
substances, we see how the carbon has become subordinated to the
hydrogen part of the compounds, with the result of rendering them more
or less unstable in their character. As Professor M'Gee has shown us,
there is in truth a graduated series leading us from the marsh gas and
rock gas as the lightest members of this class of compounds onward
through the semi-gaseous naphtha to the fluid petroleum, the
semi-fluid tar, the solid asphaltum, and the rigid and brittle
substance known as albertite, with other and allied products. Having
said so much regarding the chemistry of the fuels of the future, we
may now pass to consider their geological record. A somewhat curious
distribution awaits the man of science in this latter respect. Most
readers are aware that the geologists are accustomed to classify
rocks, according to their relative age, into three great groups, known
respectively as the primary, secondary, and tertiary periods. In the
secondary period we do not appear to meet with the fuels of the
future, but as far back as the Devonian or old Red Sandstone period,
and in the still older Silurian rocks, stores of gas and petroleum
abound. In the latest or tertiary period, again, we come upon nearly
all the forms of fuels we have already specified.
The meaning of this geological distribution of the fuels is entirely
fortuitous. Dr. M'Gee tells us that as their formation depended on
local conditions (such as plant growth), and as we have no means of
judging why such local conditions occurred within any given area, so
must we regard the existence of fuel products in particular regions as
beyond explanation. Of one point, however, we are well assured, namely
that the volume of the fuels of the future is developed in an inverse
proportion to their geological age. The proportionate volume, as it
has been expressed, diminishes progressively as the geological scale
is descended. Again, the weight of the fuels varies directly with
their age; for it is in the older formation of any series that we come
upon the oils and tars and asphaltum, while the marsh gas exists in
later and more recently formed deposits. Further geological research
shows us that the American gas fields exist each as an inverted trough
or dome, a conformation due, of course, to the bending and twisting of
the rocks by the great underground heat forces of the world. The
porous part of the dome may be sandstone or limestone, and above this
portion lie shales, which are the opposite of porous in texture. The
dome, further, contains gas above, naphtha in the middle, and
petroleum below, while last of all comes water, which is usually very
salt. In the Indiana field, however, we are told that the oils lie
near the springing or foundation of the arch of the dome, and at its
crown gas exists, and overlies brine.
A very important inquiry, in relation to the statement that upon the
products whose composition and history have just been described the
fuel supply of the future will depend, consists in the question of the
extent and duration of these natural gas and oil reservoirs. If we are
beginning to look forward to a time when our coal supply will have
been worked out, it behooves us to ask whether or not the supply of
natural gas and oil is practically illimitable. The geologist will be
able to give the coming man some degree of comfort on this point, by
informing him that there seems to be no limit to the formation of the
fuel of the future.
Natural gas is being manufactured to-day by nature on a big scale.
Wherever plant material has been entombed in the rock formations, and
wherever its decomposition proceeds, as proceed it must, there natural
gas is being made. So that with the prospect of coal becoming as rare
as the dodo itself, the world, we are told by scientists, may still
regard with complacency the failure of our ordinary carbon supply. The
natural gases and oils of the world will provide the human race with
combustible material for untold ages--such at least is the opinion of
those who are best informed on the subject. For one thing, we are
reminded that gas is found to be the most convenient and most
economical of fuels. Rock gas is being utilized abroad even now in
manufacturing processes. Dr. M'Gee says that even if the natural
supply of rock gas were exhausted to-morrow, manufacturers of glass,
certain grades of iron, and other products would substitute an
artificial gas for the natural product rather than return to coal. He
adds that "enormous waste would thereby be prevented, the gas by which
the air of whole counties in coke-burning regions is contaminated
would be utilized, and the carbon of the dense smoke clouds by which
manufacturing cities are overshadowed would be turned to good
account." So that, as regards the latter point, even Mr. Ruskin with
his horror of the black smoke of to-day and of the disfigurement of
sky and air might become a warm ally of the fuel of the future. The
chemist in his laudation of rock gas and allied products is only
re-echoing, when all is said and done, the modern eulogy pronounced on
ordinary coal gas as a cooking and heating medium.
We are within the mark when we say that the past five years alone have
witnessed a wonderful extension in the use of gas in the kitchen and
elsewhere. It would be singular, indeed, if we should happen to be
already anticipating the fuel of the future by such a practice.
Whether or not this is the case, it is at least satisfactory for
mankind to know that the mother earth will not fail him when he comes
to demand a substitute for coal. I may be too early even to think of
the day of extinction; but we may regard that evil day with
complacency in face of the stores of fuel husbanded for us within the
rock foundations of our planet.--_Glasgow Herald._
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