App. II. NOTE. 



497 



found impossible for travellers in the interior of a continent to 

 be assisted in this manner ; consequently all heiglits of African 

 stations lately published, determined from similar observations, 

 are liable to an uncertainty ranging from + 200 feet, on account 

 of this constant varying pressure of the atmosphere. From this 

 it can be easily seen that the absolute and relative heights of 

 stations on a river near the sea-level, must be subject to apparent 

 inconsistencies, or at least to irregularities, if the observations 

 be faithfully made and computed. 



Edton Dunkin. 



