hU Prof. R. Threlfall and Mr. J. F. Adair. On the 



while a little farther on there was a strong mark giving one of tha 

 usual abnormal times. 



The result was that we obtained a normal observation, but we saw 

 that had the gauge been slightly less sensitive, or the explosion 

 slightly smaller, we should have had an abnormal observation. 



In order to obtain every satisfaction on this point, we applied 

 (during the reduction of the observations) the mathematical criteria 

 of rejection, and found that we should thus reject those observations 

 — and those only which we had already decided to reject on experi- 

 mental grounds. Altogether we rejected three experiments, involving 

 six shots, out of forty; six experiments involving ninety -two shots, 



We now pass on to discuss the smaller variations in the observations 

 which we retain. It will be remembered that at first our primary 

 object in undertaking this work was to find whether there were any 

 great irregularities or not, with a view to finding whether the 

 directed action " already commented on existed to any great extent, 

 If it did, we hoped to find considerable deviations in the velocity, 

 principally above the mean. 



The result has shown, however, that while such irregularities do 

 certainly exist to a slight extent, we have no evidence to show that- 

 directed action takes place from the explosion of freely suspended 

 cartridges. The result would probably have been different if we had 

 endeavoured to produce such directed action by the application of 

 properly disposed obstacles or air spaces round the detonating point. 

 We think that the small deviations, such as they are, are real, and do 

 not depend on the gauges or chronograph, and certainly not on our 

 measurement of the plates, which was always pushed to a much 

 higher degree of certainty. It seems probable to us that though the 

 directed action is small, it exists to some extent. The observations 

 themselves afford strong proof of the fact that waves of great energy 

 travel faster than sound, and, indeed, in free water, at all events (and, 

 of course, we have no opinion beyond), the velocity is greater the 

 greater the amount of energy transmitted. If it happens, therefore, 

 that in any experiment the direction of greatest action coincides 

 with the line passing from the shot through the two stations, we shall 

 have that explosion register an abnormally high velocity. On the 

 contrary, if the energy escapes away from the piles, we shall get a 

 velocity correspondingly low. In intermediate directions of escape, 

 the velocity will be intermediate. 



A somewhat delicate question presents itself as to the precise 

 method by which these big waves may be considered to become 

 extinguished. A preliminary question which might Very well be 

 asked would be as to whether the increase in the velocity is to be 

 looked for as depending on a greatly increased adiabatic resilience. 

 We do not think that any probable change in the resilience would 



