The “cracking” process of distillation briefly consists in distilling the oils at a temperature higher than the normal boiling points of the constituents it is desired to decompose, and, in practice, the result is that the heavier oils are turned into lighter hydrocarbons of lower boiling points: thus the yield of the more valuable of the refined products is materially increased. The “cracking” process, which very largely obtains to-day, was quite accidentally discovered by a small refiner in America many years ago. The man in charge of the still left it with the intention of returning very shortly. He was, however, absent for several hours, and to his dismay found that; as the result of his neglect in attending to the still, a very light coloured distillate of much lower density than that which it was usual to obtain, was issuing from the condenser. Upon investigation, it was found that a portion of the distillate had condensed upon the upper part of the still, which was cooler, and had dropped back into the still, where the temperature was sufficient to produce products of a lower boiling point--certainly a distinct improvement. As may be imagined, this “cracking” process does not commence until the lighter products of distillation have been removed, and is now so popular because by its use a greater yield can be obtained of those more valuable products for which there is an ever-increasing demand. It is unnecessary here to enter into those various improvements which have been introduced from time to time, all of which have as their aim the production of larger quantities of refined oils, and it would likewise be invidious to enumerate even the more popular scientists to whose energies much of the resulting progress has been due, for the simple reason that it has ever been the aim of the petroleum chemist to turn his abilities in the direction indicated.