It is not practical, however, to obtain free gas in all localities ; but in all coal-fields gas may be obtained by boring to the proper depth, even in the anthracite regions where petroleum does not exist ; but there it would be very deep. In localities where subterranean gas cannot be obtained, both gas and oil may be produced from coal with more economy than oil can be supplied under present development: but our impression is that our resources of hydro-carbons, in the shape of petroleum and petroleum gases, principally within the Alleghany coal-field, are equal to any demand, and that oil pro duced from gas may yet supply light to cities and towns, villages and private houses, with more economy than it can be produced from the richest cannel coal.
We before observed that both the carbon and the bitumen of coal may be reduced to vapor or gas, and that this may be condensed in the shape of oil. The manner of con verting subterranean gas to oil would be nearly similar to that employed in the re duction of coal-gas, and the chemical action is a close imitation of the processes of nature, in which water and air act principal parts, while heat and cold, in combination with mechanical power, expands or condenses the coal or the gas. The modus operandi and the mechanical means are not necessarily confined to one single mode. Every chemist and mechanic knows how various are the processes or modes frequently used in accomplishing the same object.
The aim of the practical and experienced is always towards economy and simplicity. One mode may be very beautiful and attractive in theory, but very expensive and profit less in practice. It is, therefore, of the first importance that the simplest and most economical modes and processes be employed in all practical operations when they can be made available; but, as before stated, we cannot here illustrate the various modes of distilling coal-oil now in use, or those which may be more available; while the process of condensing or utilizing petroleum gases would be still more difficult to explain for practical purposes in the space now at our command. The hints we have given may set practical men to thinking, and to an investigation of the subjects discussed, and which may lead to useful results. We propose, however, to elaborate these subjects fully in a future publication, when experiments now in process of operation shall have demonstrated the most practical processes both of the distillation of coal and the con densation of gas.
The modes now practised for the distillation of coal and other bituminous substances, and the production of coal-oil therefrom, are both expensive and wasteful ; while the refining of the crude oil, whether petroleum or coal, is complicated, costly, and im perfect.