III.—-Meteorological, etc., Observations. 
valuable studies on Ruwenzori. But if the data have nevertheless been referred 
to Bujongolo, it was because they offered greater guarantees of accuracy, and 
this for the following reasons :— 
First of all, the difference of altitude between Bujongolo and Fort Portal 
may be regarded as near enough, having been obtained from a considerable 
number of observations. On this account we may consider as partially com¬ 
pensated those sources of error which are due to atmospheric disturbances, 
such as may have a great influence on isolated measurements, especially when 
dealing with very remote stations. Such would precisely have been the case if 
the data observed on Ruwenzori had been directly compared with those 
corresponding hour for hour with Fort Portal. But by making the comparisons 
with the data obtained at Bujongolo, a much nearer place, one may fairly 
assume a greater uniformity of atmospheric conditions. 
Then there is another fact which shows the greater convenience of the 
course adopted. It is seen in the following example to which many others 
might be added. 
On 7th July, at 12 o’clock, on Edward Peak, the pressure (reduced to 0°) 
was 428 - 5 mm., and the temperature 1°’6 Celsius (34°*4 F.), the corresponding 
readings being at Bujongolo 489T6 mm. and 3 0, 9 Celsius (39° F.), and at Fort 
Portal 638 - 69 mm., and 23° - 3 Celsius (74° F.). 
Calculating from these data the difference of level between Edward Peak 
and Fort Portal, and then separately between Edward Peak and Bujongolo, and 
between Bujongolo and Fort Portal, we get:—* 
Difference of level between Edward Peak and Fort Portal ... 3,355 metres 
Difference of level between Edward Peak and 
Bujongolo ... ... ... ... ... 1,074 metres 
Difference of level between Bujongolo and Fort 
Portal... ... ... ... ... ... 2,249 „ 
Total difference of level between Edward Peak 
and Fort Portal ... ... .. ... 3,323 metres (10,900 feet) 
Therefore, with the direct calculation, and omitting Bujongolo, we have a 
difference of over 32 metres (105 feet). 
Such a difference arises from the fact that whereas the law of Laplace 
is based on the hypothesis of a static ecpiilibrium of the atmosphere, and of 
a temperature and humidity which decrease regularly with the altitude, this 
does not take place in the present instance. 
* In this estimate no account is taken of the tension of the aqueous vapour. 
369 2 B 
