124 TERRESTRIAL MAGNETISM. 



declination, had occasioned me to institute, in the harbour 

 of Cumana, a series of careful observations. "Prom the 

 1st to the 2nd of November the inclination continued with 

 great steadiness to show a mean amount of 43'65. The 

 instrument remained untouched and properly levelled, in 

 the same place. On the 7th of November, three days after 

 the strong earthquake shocks, the instrument, after being 

 levelled afresh, gave 42*75. The intensity of the magnetic 

 force, measured by vertical oscillations, was unaltered. I 

 hoped that the inclination would return, perhaps gradually, 

 to its former value ; but it remained the same. On return- 

 ing to Cumana in September 1800, after travelling by 

 river and land journeys on the Orinoco and Eio Negro 

 upwards of two thousand geographical miles, the same 

 dipping-needle of Borda's, which had accompanied me every- 

 where, gave the inclination 42*80, very nearly the same as 

 in the last observation before it left Cumana. As mechanical 

 agitations and electric shocks, by altering the molecular con- 

 dition in soft iron, elicit poles, so we may conceive it possible 

 that there may be a connection between the direction of 

 magnetic currents and that of earthquake shocks; but 

 although my attention was strongly directed towards a 

 phenomenon of the objective reality of which I had in 

 1799 no reason to doubt, yet, in the numerous earthquake 

 shocks which I experienced during the three years subse- 

 quently passed in South America, I never again met with a 

 sudden alteration of the magnetic inclination which I could 

 ascribe to such a cause, various as were the directions in 

 which the undulatory movement of the terrestrial strata 

 was propagated. A very accurate and experienced observer, 



