ALTHOUGH great progress has been made during recent years in the electrification of collieries, about one third of the total power utilised is still generated mechanically. According to the Electrical Review of June 29, the total horse-power of the motors in use in collieries is now about 1,900,000. This is equivalent to more than ten per cent of the capacity of all the plant connected to the public supply mains in Great Britain. Of the electricity used, only about thirty per cent is supplied by statutory authorities. Doubtless this percentage will rapidly increase, as power can be produced more cheaply at points away from the pithead where a more abundant water supply is available for condensing purposes. It is satisfactory to notice that, despite the increase in the use of electricity, the number of electrical accidents is steadily decreasing. This is due to the design of flame-proof structures and flame-proof apparatus. Owing to the high standards adopted by the Association of Mining Engineers, the costs of maintenance have also rapidly diminished. The fixing of minimum standards for illumination for portable lamps is a notable advance. We think that inventors ought to turn their attention to the development of a fixed lighting system which would be safe to use at all parts of the coal face.