666 Proceedings of the Royal Society 
tions from south round to west, the case is that of a high district, 
with currents of moist air poured in upon it, and the consequence 
is, an enormous rainfall, amounting, for example, at Grlencroe to 
128 inches, and at the head of Lochlomond to 115 inches. Between 
these extremes the amount of the rainfall varies, the variations 
being dependent on the physical configuration of the surface. 
The monthly average rainfall has been examined by the dis- 
cussion of observations made at 126 places for long terms of years 
— the number of years varying from 10 to 60, and the whole averag- 
ing 21 years. Of the stations dealt with, 54 are on the west slope, 
and 72 on the east slope. The mean annual rainfall for the whole 
country, deduced from these averages, is 44 inches ; for the eastern 
slope 38 inches, and for the western slope 50 inches, — amounts 
which are probably not far from the true averages of these different 
regions. 
In December, the general average for the whole country is 
greatly above the average monthly fall; in May it falls to the 
minimum, after which it continues to increase till it again rises 
considerably above the monthly average in October, to fall again, 
however, to about the average in November. The curve of the 
rainfall of the east, as compared with that of the west, shows the 
wet and dry seasons to be less strongly marked in the east; or the 
departures from the monthly averages are larger in the west. 
Since, however, the curves closely resemble each other, the general 
causes bringing about the deposition of rain in the west and in the 
east are the same. But at all seasons the absolute amount of the 
rainfall is greater in the west than in the east. 
The largest monthly rainfall takes place in December in the 
north-western and western districts, and in the mountainous dis- 
tricts of the interior ; in January , in the south-west, the Ochil Hills, 
and east of Perthshire ; whereas, at a number of places in the drier 
districts, August is the month of largest rainfall. 
The month of least rainfall is April , in the south of Scotland, 
May in the north, and June in Orkney, Shetland, and Faro; and 
it is remarkable that these same months are the months of largest 
(or very large) rainfall in various extensive regions on the continent 
of Europe. 
