314 



PKOF. W. A. BONE AND OTHERS ON 



high initial pressures. But in this we were not entirely successful, owing to the 

 excessively short intervals between ignition and the attainment of the maximum 

 pressure, more particularly in the case of the fastest burning of the mixtures referred 

 to, namely, 2H 2 + O 2 . It was decided, therefore, to limit the investigations to the 

 study of corresponding " air " mixtures, whose composition may, for all practical 

 purposes, he written 



2H a +0 3 +4N 3 , 



.+4N2. 



The experimental method consisted in firing such mixtures at initial pressures 

 of from 45 to 50 atmospheres in the spherical bomb, B, to which was attached 

 a Petavel recording manometer with its optical accessories. 



The action of this manometer depends on the principle that the time period of a 



Fig. 14. 



vibrating system may be expressed in terms of W the weight of its moving parts, and 

 A the force required to produce unit deflection therein, as follows, 



Vw 

 -, 

 Kg 



and in order to make Q as short as possible, consistent with a sufficiently great 

 strength (W) to withstand the sudden development of extremely high pressures, the 

 controlling force (A) brought into play per unit length of motion is made as great 

 as possible, by using the stiffest spring obtainable. This means, of course, that the 

 actual motion produced in the spring by the explosion is exceedingly small, but for 

 recording purposes this is magnified by a special optical device, which focuses a point 

 source of light on to a rapidly revolving drum, to which is attached a sensitive photo- 

 graphic film. 



The following description of the instrument (fig. 14) used in our experiments is 



