“White damp” is a more dangerous gas than either of the others, but is not so frequently found. It is carbonic oxide, and consists of equal portions of carbon and oxygen. It is a very little lighter than air, and has a tendency to rise. When present in a sufficiently pure state it burns with a blue flame, but ordinarily it is incombustible and produces no effect upon the flame of the lamp. It is tasteless and odorless, and its presence cannot be detected before it has done its dangerous work. To breathe an atmosphere containing a very small percentage of it will speedily produce a fatal result. It acts on the system as a narcotic, and its effect is produced even more quickly than is that of black damp. It is not thought to be given off in appreciable quantities by the coal at the open faces; but it is formed when the carbonic acid passes through any ignited carbonaceous material, or when steam passes over burning coal. It is therefore produced most frequently by smouldering gob fires, by burning wood in the mines, or by a shaft on fire, and may exist as one of the results of an explosion of fire damp or of blasting powder. It is the most to be dreaded of any of the gases which the miner has to encounter. He may possibly avoid the surging flame of the fire damp, he may escape from the falling after damp, and make his way unharmed through bodies of black damp lying thick about his feet, but if he has still to encounter this terrible white damp his good fortune will have been of little avail; death will almost surely seize him. In connection with this may be mentioned the fact that under certain conditions coal dust may become violently explosive. When it is mixed with air, with or without the presence of fire damp, and is set into sudden and intense vibration by a heavy powder blast, a fall of roof, or other means, it may explode with greater destructive force than even fire damp is capable of. Happily such explosions are not frequent, all the conditions necessary being rarely present at the same time. It is obvious, moreover, that an accident of this kind could occur only in a very dry mine. It is true also that the dust of bituminous coals is much more liable to be explosive than the dust of anthracite. No well authenticated instances of coal dust explosions have been reported from the anthracite regions, while in mining soft coals they have undoubtedly occurred. Two cases of this kind were reported from France, one in 1875 and one in 1877. No longer ago than November 9, 1888, a terrible explosion of coal dust occurred in a bituminous coal mine at Pittsburg, Kansas, by which more than one hundred lives were lost.