The author describes an apparatus by means of which the explosive power of gaseous combinations can easily be determined, and from this, by Bunsen process, the temperature may readily be calculated. The essential feature of the apparatus is the registration of the ‘compression volume’ of a given initial volume of air, on which the gaseous explosive mixture has been allowed to act. As the duration of the pressure is all but instantaneous, the well-known formula

may be employed to ascertain the final pressure, more especially as the sudden rebound prevents any great loss of heat.