127 



Besides, the two instruments are not founded 

 precisely on the same principle ; for the artificial 

 magnet having a quantity of fluid, which is as it 

 were independent of that of the Earth, it may be 

 conceived, that the magnetometer, conveyed to 

 different climates, cannot give the same results 

 as the oscillatory apparatus. 



In speaking of the physical observations made 

 during the passage from Perrol to Cumana, 

 I have not mentioned my experiments on the 

 purity of the air, and it's electric charge*. The 

 former were made by means of the nitrous gas 

 in the narrow tubes of Fontana's eudiometer, 

 and seemed to indicate a greater portion of oxy- 

 gen in the strata of the atmosphere lying on the 

 sea, than in those which surround continents. 

 We know at present, that, if eudiometrical vari- 

 ations exist, they must be less than two thou- 

 sandths ; and that the results I obtained in 

 1799 do not merit confidence, on account of the 

 too imperfect means then employed in the ana- 

 lysis of the atmosphere. 



* I took the greater interest in this kind of experiments, 

 because, a short time before my departure from Germany, I 

 had devoted myself to a very extensive inquiry into atmo- 

 spherical electricity at the foot of the high mountains of Salz- 

 burgh. The results of my labours arc related in the Journal 

 4e Physique, an 7. 



