form of recuperating the yield of oil. As the process of increasing the production of Petroleum in oil wells, by means of the explosion of gunpowder or its equivalent, substantially as described in the specification of E. O. L. Roberts, ante-dated May 20, 1866, was claimed by the patentee to cover the use of Nitro-Glycerin and every known or hereafter to be invented method of effecting an explosion in an oil well, and as the case has hereto been presented in the courts, this claim has been sustained. When, therefore, the contractors commenced operations on their work at the Tunnel, I resumed my manufacture of Nitro-Glycerin for that work, leaving the oil region, where the oil operators and producers have since been incessantly litigating the validity of the Roberts patents above referred to, with, however, up to the present date, indifferent success. The average of greatly increased production in exhausted wells, so far as my experience extended, during four months at one hundred wells, was that 80 per cent. were benefited, and in about 20 per cent. no marked results were obtained. When the question as to whether this form of blasting, viz.: in oil wells, is patentable has been decided, it will be time to renew the careful application of Nitro-Glycerin in oil wells, but at present, the careless handling, the pursuit of wealth regardless of the lives of the employed, and the unscrupulous assertion prevalent among those interested in the patent referred to, is depriving the oil producers of a valuable agent. Since, however, the present yield of oil is ample for the consumption, this, so far as the public is concerned, is of less moment than it is to the producers, who, by the time economical and useful blasting in oil wells is needed to bring up the yield to the ever increasing demand, will have finally disposed of this patent litigation. [Illustration] CHAPTER III. Nitro-Glycerin Considered in its Chemical Details.