Chapter VII. 



month, from the 16th of June to the 12th of July. In this way 

 the altitude of Bujongolo was established at 7,435 feet above 

 Fort Portal, consequently 12,461 feet above the sea-level. Tbe 

 observations taken in the valleys and on the peaks with the 

 mercurial barometer, or in places of secondary importance with 

 the aneroid, were then referred to this base. A third base 

 of less value, because the observations there were not taken 

 during so long a period as at Bujongolo, is Ibanda in the Lower 

 Mobuku Valley. Only one of the measurements of altitude 

 refers to tliis as its base point, namely, that of the Iolanda 

 Peak of Mt. Gessi, which was also taken with the boilino-- 

 point thermometer because the barometer was broken. 



To estimate the approximation to the actual trulli, which 

 may be attained by measuring heights merely by direct obser- 

 vation of atmospheric pressure, by means of the boiling point 

 of water (hypsometer), or by the aneroid barometer, it will 

 sufiSce to compare some results obtained by this simple method 

 with the corresponding measurements as taken by the Duke 

 and calculated witli all the corrections furnished by a base 

 station. 



220 



