Still later, viz. about 1767, we have the Rev. R. Watson, D.D., Regius Professor of Divinity in the University of Cambridge, and Bishop of Llandaff, interesting himself in chemistry. He wrote a series of _Chemical Essays_, one of which is entitled, _Of Pit Coal_, and in this he describes the production from coal (by destructive distillation) of illuminating gas, ammonia-water, tar, and coke. He further compares the relative quantities of the different products from various kinds of coal, but he appears to have been chiefly interested in the tar, and disregarded the gas and other products. Not the least interesting part of his book is the preface, in which he apologizes for his pursuits in the following words-- "Divines, I hope, will forgive me if I have stolen a few hours, not, I trust, from the duties of my office, but certainly from the studies of my profession, and employed them in the cultivation of natural philosophy. I could plead in my defence, the example of some of the greatest characters that ever adorned either this University or the Church of England." This is quoted from the 5th edition, dated 1789, the essay on coal being in the second of five volumes. As the learned bishop published other works on chemistry, we may suppose that the forgiveness which he asks from his brother divines was duly accorded. None of these preliminary experiments, however, led to any immediate practical result so far as concerns the use of coal-gas as an illuminating agent. Towards the end of the last century the lighting of individual establishments commenced, and the way was thus prepared for the manufacture of the gas on a large scale. One of the earliest pioneers was the ninth Earl of Dundonald, an inventive genius, who in 1782 at Culross Abbey became one of the first practical tar distillers. He secured letters patent in 1781 for making tar, pitch, essential oils, volatile alkali, mineral acids, salts, and cinders from coal. The gas was only a waste product, and, strange as it may appear, the Earl, whose operations were financial failures, did not realize the importance of the gas, the tar and coke being considered the only products of value. Here is the account of the experiments by his son, Admiral Dundonald, the Sailor Earl, quoted from his _Autobiography of a Seaman_:--