252 



adjust and verify the instrument. It marked*, 

 after I had well rectified the level, 325*4 lines, 

 at the temperature of 25 *4°, at half after eleven 

 in the morning. I attach some importance to 

 this observation, because, in order to know the 

 configuration of a continent, it is more useful 

 to determine the height of plains two or three 

 hundred leagues distant from the coast, than 

 to measure the peaks of the Cordilleras. A 

 barometric determination made at Sego on the 

 Niger, at Bornou, or on the table lands of Kho- 

 ten and of Hami, would be more interesting 

 for geology than the measurement of the moun- 

 tains of Abyssinia and of Musart. The horary 

 variations of the barometer take place in the 

 forests of Javita at the same hours as on the 

 coast, and at the farm of Antisana, where my 

 instrument was suspended at the height of 

 two thousand one hundred and four toises. 

 They were from nine in the morning till four in 

 the afternoon 16 line. The 4th of May they 

 were even nearly two lines. The hygrometer 

 of Deluc, reduced to that of Saussure, kept 



* The remark made on the correction of the basin (chap. 

 ]7, vol. iv, p. 378, note) is applicable to the heights which I 

 have indicated, vol. iv, p. 455, 555, and 572 ; and p. 85 of 

 the present volume. These heights indicate only relative 

 differences. I believe I have estimated a little too high 

 (Obs. Astr., vol. i, p. 298) the absolute elevation of May- 

 pures. 



