Earthquake-wave Transit. 359 



enormous discrepancies between the results of observations 

 made at different points along the range from Hallet's Point 

 are reconcilable by taking into account the difference in mag- 

 nifying-power of the different seismoscopes there employed. 

 It seems to me, however, that this proposed explanation, if 

 critically examined, would be found wholly insufficient to 

 account for the enormous discrepancies between the observa- 

 tions made at the several stations, still less to reconcile the 

 transit-velocities recorded with the well-established and inter- 

 dependent physical conditions of the transit of sound, or ana- 

 logous elastic waves, in liquids and solids. 



Few physical data have been better established experimen- 

 tally than the rate of transit of sound in water (approximately 

 about 4700 feet per second), as determined by Colladon and 

 Sturm in the Lake of Geneva, and confirmed by Wertheim by 

 a different method. Yet the transit-velocity in discontinuous 

 water-logged shingle is given by observation No. 5 at 5309 

 feet per second; and it is suggested that the rate is increased 

 by the presence of the water. How these conditions are re- 

 concilable with each other, or with the well-known physical 

 conditions by which the circumstances of transmission of 

 sound are interdependent and linked together, I am unable to 

 imagine. The proposed smoothing-down of the discrepancies 

 by referring them to the differences in magnifying- power of 

 the seismoscopes employed is insufficient to account for dis- 

 crepancies so enormous ; and the proposed explanation seems 

 to me only to amount to this — that if different observers note 

 the instant of arrival as indicated by different parts of the same 

 seismoscopic wave, they will necessarily obtain discordant 

 results, and such as, in my judgment, no ingenuity of discus- 

 sion of the observations recorded can reduce to the position of 

 reliable scientific data. 



It is with surprise and disappointment that I find General 

 Abbot has not acquainted himself with the magnifying-power 

 of the seismoscope constructed by me and employed in all 

 my experiments; and so little does he seem to have ac- 

 quainted himself w r ith the scientific literature of the subject 

 before he himself commenced to work upon it at Hallet's 

 Point, that I am compelled to suppose my published de- 

 scription of that instrument, and all my earlier researches, 

 which were not communicated to the Boyal Society, but were 

 published by the British Association for the Advancement of 

 Science, remain even now unknown to him. My seismoscope, 

 which is that w T hich I have employed in all my subsequent 

 researches, General Abbot will find described by referring to 

 my " Second Report on the Facts of Earthquake Phenomena," 



