ON THE FACTS OF EARTHQUAKE PHiENOMENA. 



293 



The whole distance is half a inile=2640 feet ; hence the gross ratio of 

 transit per second^is — 



2"-911639 : 2640 :: l"-000000 : x ^^^^^^^dO&IOS feet per second. 



2-911639 

 This has to be corrected for — 



1st. Time of transit of the electric force along the wires of releasing and 



of firing. 

 2nd. Time of half-transit of the mercurial wave in the trough of the 

 seismoscope, i. e. half the whole time of raising and transmitting 

 this wave. 

 3rd. The personal equations of both observers. 



And possibly a correction may arise from the time actually consumed in 

 the progress of the explosion of each mine ; for although an explosion conveys 

 popularly the notion of instantaneous or momentary action only, yet, as we 

 shall see, a very appreciable time is required to explode {i. e. consume) a 

 large mass of powder. 



The following experiments were undertaken to provide for this contin- 

 gency ; and having stated their results, I shall reserve the application of any 

 corrections until after the description of our further experiments made in the 

 granite. 



Table No. 3. 



Showing the whole time of " hang fire," from the moment of contact to that 

 of explosions in primings and service charges. — Note. The results are all 

 in the smallest divisions of the small dial, each =0"-014206. 



