324 



quake. This was expressed by 229 oscillations 

 in 10 minutes of time, when at Madrid it was 

 240, at Paris 245. On the 7th of November I 

 ascertained the magnetic variation ; which I 

 found to be 4° 13* 50" east. I had found it 

 before the earthquake, at different hours of the 

 day, from five to six minutes greater and less. 

 The horary variations conceal the effects of 

 changes in the variation, when these are not 

 very considerable. 



Reflecting on the whole of these magnetical 

 phenomena I am not aware of any cause of 

 error, that could have changed the result of 

 my observations of the dip, made before the 4th 

 of November. I employed the same precau- 

 tions, I did not change the place of the instru- 

 ment -jf, and I noted in my journal the parti- 

 culars of each observation. It is indeed very 

 remarkable, that the needle kept with the great- 

 est care in oiled paper, after a journey of seven 

 hundred leagues, on our return to Cumana 

 gave, on taking a mean of fifteen observations, 



* On the 28th of August, 1799, dip toward the east, 

 42*97°; toward the west, 44-10°. On the first of Nov., 

 east 43 10° ; west 44*20°. On the 7th of Nov., east 42' 15° ; 

 west 43-35°. On the 6th of September, 1800, east 42*20°; 

 west 43*40°. 



t Mr. Gay-Lussac and myself found in 1805, changing 

 the poles m each place, at Milan 66° 46 1 in the town, and ia 

 a field near the town, 66° 36', of the old division. 



