Minerals remained for the most part unworked, though the profitable coal fields and oil wells in Ferghana were used when disturbances in Trans-Caspia cut Turkestan off from the Baku oil, on which it relies entirely for its industrial life.
In a modified degree the same is true of the Indian fields; large supplies are unworked, but in several districts, especially about Raniganj and elsewhere in Bengal, workings are fully developed.
Similarly in Siberia and Japan there are extensive supplies unworked or only partially exploited.
Shows the quantity of coal still remaining unworked in the different coalfields at depths not exceeding 4000 f t.
The ground is then left unworked and open to the crumbling influence of frost till towards the end of winter, when it is stirred with the cultivator followed by the harrows, or in some cases ploughed with a shallow furrow.