Appendix B„ 
brought with us on these excursions were:—a Fortin barometer which had for 
a long time been compared with another left at Bujongolo ; an aneroid likewise 
compared with the two Fortins ; a thermometer for taking the temperature of 
the air, and two hypsometric thermometers. 
For the more important points, for instance, for nearly all the peaks, and 
always where possible, the measurements of pressure were made with the 
mercurial barometer, the aneroid being used only in a few special cases where 
it would have been very difficult to carry, or take measurements with the 
mercurial barometer, and also for places of secondary importance. The 
precaution, however, was taken to take down or record the indications of the 
aneroid even whenever the Fortin was used. 
Not till after 12th July, when the Fortin got damaged, was the hypsometer 
employed. Whenever it was possible, the observations were made at the same 
hours as those of Bujougolo (9, 12, and 17), but occasionally this was not 
possible, and then we assumed as terms of comparison the data of Bujongolo 
made at the nearest hours, unless there were reasons for adopting the mean 
of two consecutive data. 
In connection with this preferable choice of data for the calculation of 
altitudes it should be noted that for places for which the daily variation of 
pressure, temperature, etc., is known, that is to say, where the hour of the 
maxima and minima and the extent of the daily variations are ascertained, it 
is possible to reduce a determination made at any given hour to another 
determined hour. But in the present case these fundamental notions are 
lacking, and for regions such as that under consideration, meteorological studies 
are too rare to enable us confidently to extend to them those laws that have 
been established for regions of the temperate zone.* 
For Bujongolo we should no doubt have some element to establish 
approximately the daily movement of pressure, temperature, etc., but the same 
cannot be said for the other places in Kuwenzori, and especially for the peaks. 
For these reasons the heights were calculated with the data, such as they 
were, without modifying them in any way on the ground of the hours when 
the observations were made. 
Another matter, which, however, has no great influence, is that concerned 
with the humidity, or rather the tension of the aqueous vapour which is always 
* Let one example suffice to show what caution is necessary in this respect. At 
Bujongolo the mean pressure at 9 o’clock is 488'87 mm. (see Table VIII, 6) ; at 12, 4S8'67, 
and at 17, 4S8'08, so that the maximum of the morning is reached before midday, and 
at this hour the barometer is already falling. On the other hand on the Santis Peak 
(2,467 metres), the maximum of the morning is delayed till toward 14 o’clock, and on Mt. Blanc 
(4,811 metres), till towards 15 (Angot, meteorologie). 
366 
