14 Proceedings of Royal Society of Edinburgh. [dec. 6, 
The high expectations formed of the great importance of this 
Observatory have already been more than realised. The following 
are among the more prominent of the results obtained from this 
pair of high and low level stations : — 
1. The rate of decrease of temperature with height has been 
more correctly ascertained. 
2. The rate of decrease of atmospheric pressure with height for 
the different sea-level pressures and air-temperatures has been ascer- 
tained with a high degree of accuracy. 
3. The relations of the readings of the dry and wet bulb hygro- 
meter to the vapour of the atmosphere have been worked out, under 
the extraordinarily dry states of the air which are of such frequent 
occurrence on the top of the mountain, from observational data to 
a degree of accuracy not hitherto attained. 
These results will, doubtless, in future be incorporated in all 
books on meteorology and general physics. 
As regards weather forecasting, the Ben Nevis observations con- 
tribute information of such a value as no low-level observatory, 
however efficiently equipped and superintended, can for a moment 
lay claim to ; and it is to be enforced here, that when the Directors 
are placed in a position to raise the five daily observations at Fort 
William to twenty-four, the value of the Ben Nevis observing 
system will be immensely enhanced. In other words, the Directors 
of the Observatory attach the greatest importance to the establish- 
ment of a low-level observatory at Fort William, at which observa- 
tions could be made with the same fulness as at the Observatory on 
the top of the mountain. 
The great value attached to the observations of high-level observa- 
tories is attested by the continued additions made to these stations 
in different parts of the world, and by the observations made at 
these stations many of the more important questions of meteorology 
may doubtless be investigated. But there is no other high-level 
observatory, and its conjoined low-level station, so happily situated 
as Ben Nevis Observatory and the station at Fort William for sup- 
plying physicists with observational data. This is due to the fact 
that the former is on a peak and the latter close to the sea, the 
ground sloping down to it, hy which the effects of solar and terres. 
trial radiation are minimise'!. 
