IGO 



REPORT — 1895. 



From the above data it is clear, as Abbot sliows, that the rate at 

 ■which a shock is transmitted increases with the intensity of the initial 

 explosion ; that when a high magnifying power has been used, tremors in 

 advance of those revealed by a low power have been noticed, with the 

 result that the apparent velocity in the former case is greater than in the 

 latter ; and that the velocity of propagation has been higher through rock 

 than through soft material like drift. 



A query put forward by Genei-al Abbot is whether still higher velocities 

 would have been recorded had telescopes with a greater magnifying power 

 been used. The answer is apparently in the affirmative, and therefore if 

 we wish to compare the observations amongst themselves, not only must 

 we choose those in which the initial impulse has been the same, but where 

 the observers have employed similar instruments. Comparing observation.^ 

 10 and 1 2, but not overlooking the fact that No. 10 was largely transmitted 

 through water, and again 16 and 17, it might be concluded that as a 

 wave advances its velocity is diminished ; but from the first five observa- 

 tions it would seem that there is at the commencement an increase in the 

 initial velocity until it reaches a maximum, after which there is a 

 diminution. This increase in the rate of transmission at the outset of a 

 wa\e from its origin is again seen in experiments 9 and 11. The difference 

 in the velocities recorded for experiments 18 and 19 may be due to the 

 fact that in the case of the shallow torpedo much of the initial energy was 



