The conversion of coal into coke is a very venerable branch of manufacture, which was first carried out on a large scale in this country about the middle of the seventeenth century. As an operation it may appear utterly devoid of romance, but as Goethe has described his visit to the earliest of coke-burners, this fragment of history is worth narrating. When the great German philosophical poet was a student at Strassburg (1771), he rode over with some friends to visit the neighbourhood of Saarbruecken where he met an old "coal philosopher" named Stauf, who was there carrying on the industry. This "philosophus per ignem" was manager of some alum works, and the ruling spirit of the "burning hill" of Duttweiler. The hill no doubt owed its designation to the coke ovens at work upon it, and which had been in operation there for some six or seven years before Goethe's visit, _i.e._ since 1764. The coke was wanted for iron smelting, and even at that early period Stauf had the wisdom to condense his volatile products, for we are told that he showed his visitors bitumen, burning-oil, lampblack, and even a cake of sal ammoniac resulting from his operations. Goethe has put upon record his visit to the little haggard old coke-burner, living in his lonely cottage in the forest (_Aus meinem Leben: Wahrheit und Dichtung_, Book X). It is probably Stauf's ovens which are described by the French metallurgist, De Gensanne, in his _Traite de la fonte des Mines par le feu du Charbon de Terre_, published in Paris in 1770. After long years of coke-making, without any regard to the value of the volatile products, we are now beginning to consider the advisability of doing that which has long been done on the Continent. It is not unlikely that Bishop Watson in the last century had heard of the attempt to recover the products from coke ovens, for he gives the following very sound advice in his _Chemical Essays_:-- "Those who are interested in the preparation of coak would do well to remember that every 96 ounces of coal would furnish four ounces at the least of oil, probably six ounces might be obtained; but if we put the product so low as five ounces from 100, and suppose a coak oven to work off only 100 tons of coal in a year, there would be a saving of five tons of oil, which would yield above four tons of tar; the requisite alteration in the structure of the coak ovens, so as to make them a kind of distilling vessels, might be made at a very trifling expense."--5th ed., 1789, vol. ii. p. 351.