As may be imagined, the industry of petroleum refining has had to adapt itself to the altered conditions of to-day. For instance, prior to the advent of the internal combustion engine, which now is responsible for such a wide application of motor spirit, the demand for this, the lightest product of petroleum distillation, was non-existent. Consequently, when such spirit was produced, there was no market for it, and its production represented sheer loss to the refiners. Both in the Far East and in Russia, we have examples of the enormous loss which accrued to the refiners by reason of there being no market for this highly inflammable product. In the Far Eastern fields, in particular, this loss was very heavy, for in the earlier days of its operations, the “Shell” Company had to remove thousands of tons of this now valuable motor spirit from its refineries and burn it in the open fields. The successful introduction of the internal combustion engine, however, completely changed the aspect of petroleum refining, and the desire became general, not to see how little motor spirit could be produced, but to perfect methods by which the yield of the benzene series of hydrocarbons should be as large as possible. Even to-day progress is still being recorded in this direction, and each American refiner is vying with his neighbour as to how far that output of gasoline, as it is there called, can be increased. Many and varied are the means which have been resorted to for this purpose, but most of them have reference to improvements in the processes for refining the crude oil. One, however, is worthy of being mentioned in this little treatise, inasmuch as it deals with quite another aspect of the problem of increased motor spirit supply. As I have mentioned in another chapter, enormous quantities of natural gas exude from the oil-wells, and this in the past has been for the most part allowed to go to waste in the air, causing an ever-present danger to oil-field operations on account of its liability to ignite. Being heavier than the air itself, for it is impregnated with oil gases, it remains for long periods in the lower air strata, and, consequently, not infrequently, has been the direct cause of great oil-field fires. This gas--casing-head gas, as it is termed--comes from the oil-wells between the casing and the tubing, and, in the case of numerous wells, the flow is remarkable, some wells giving forth 300,000 cubic feet of gas every 24 hours, and the only useful purpose that this vapour has served until recent years has been to light several towns situated comparatively near to the oil-producing fields. The great volume of the gas, however, has been allowed to go to waste.