THERE are few questions so much in need of a satisfactory solution as the relationship which exists between colliery explosions and changes of atmospheric pressure. Before anything was known of the weight, and variations in the weight, of the air, before the barometer was discovered, miners had learned to connect the state of their working places with weather changes. The old pits were very shallow, the workings very limited, and the ventilation practically left to take care of itself, so that it is not difficult for us to understand the effect of temperature rather than pressure on the atmosphere of the mine. “Trefoil damp,” “pease bloom damp,” c in winter “the damps were scarcely felt or heard of.” In the early part of the present century Mr. John Buddle, the Newcastle viewer, having watched his barometer and the mining reports became strongly of opinion that “accidents from fire-damp always occur with a low barometer.” Faraday and Lyell's Report on the Haswell disaster of 1844 dwelt upon the importance of officials taking into account the variations of the barometer in the management of mines. Since then numerous public Commissions and private inquirers, English and foreign, have investigated the connexion supposed to exist between the exudation of gas and a falling barometer. The earlier decisions may be said to favour Mr. Buddie's opinion, but of late years there appears to be a tendency to declare that the effect of a low or falling barometer has been considerably over-rated—that in reality it has little or no influence. Under whatever conditions of pressure explosions formerly occurred, it is perfectly clear from the experience of recent years that disasters take place, as a rule, when there is an excess and not when there is a deficiency of pressure.