Although the calciferous sandstone series is well developed in other parts of Scotland, it has not hitherto yielded any oil-shale of economic importance beyond the limits of West Lothian, Mid Lothian, and Fife. Thin seams of oil-shale do occur in various places in the counties of Haddington and Berwick, but, generally speaking, the quantity is not sufficient to be practically worked. A word or two as to the oil-shales themselves. The shales, as known in the Lothians, are fine black or brownish clay shales, with certain special features which enable them to be easily distinguished in the field. Miners draw a distinction between “plain” and “curly” shale, the former variety being flat and smooth, and the latter contorted or “curled,” and polished or glossy on the squeezed faces. In internal structure, oil-shale is minutely laminated, which is apparent in the “spent” shale after distillation, when it is thrown out in fragments, composed of extremely thin sheets like the leaves of a book. Before touching upon the methods employed in mining the shale and the treatment it receives during distillation, it is interesting to note that the industry in Scotland has passed through many vicissitudes since its establishment. At that time, the American oil industry was but in its infancy, and the production in the States was utilized mainly on the American markets. Consequently, there was a great demand for the Scottish oils in this country, and in 1870 there were no fewer than ninety small oil-works in the Lothians, the majority of which were operating the shales. It was about this time that the American illuminating oil came over to this country, and a very sorry blow was dealt the Scottish industry. So disastrous was the resulting competition between the Scottish products on the one hand, and the American and Russian petroleums on the other, that one by one the Scottish companies closed down, and, after less than eight years of competition, the number of operating companies had fallen to twenty-six. The decay continued until the number of active concerns in the Scottish shale-oil industry could be counted on one’s fingers. The industry exists to-day simply as a result of the great improvements which have been made in the retorting of the shale, by which larger quantities of products are produced--including ammonia. It is thus able to withstand foreign competition. To-day, it is estimated that nearly 4,000,000 tons of the Scottish shales are treated every twelve months by the several operating oil companies. The most important of these concerns--the Pumpherston Oil Company--has been regularly operating since 1883, and, inasmuch as it deals with by far the largest quantities of shale treated, a brief account of its operations will be of advantage in enabling the reader to understand the methods by which a total of nearly 400,000 tons of oil are produced each year in Scotland.