FROM TONKIN TO INDIA 



L In column i are given the corrected barometric pressures with allowance for 

 tide and for the error of the aneroid. The latter was obtained from hypsometric 

 observations taken at least once a week and oftener in all important places. My 

 two hypsometers were supplied by Baudin, and their slight zero error was measured 

 at the start and verified at the finish. To guard against sudden variations in the 

 aneroids, such as might be caused by a blow, I nearly always had two about me, and 

 took simultaneous readings for every altitude. Thanks to these constant comparisons, 

 I can vouch for the exactness of the corrected pressures to within .05905 of an inch. 



