PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
207 
lower than the mean of the south-east of England. Thus 
the warmest part of England in July is included within a 
semi-circle with a diameter of 20 miles, stretching to the 
south and south-west of London, and thereforo including 
nearly all Surrey, the greater part of Berks, and part of 
Kent, and Middlesex, where the mean of July is 64"4; but 
in Scotland the isothermal line of 58 in July skirts the 
Mull of Cantyre, and goes nearly due north through Argyll 
and Inverness to the Moray Eirth, where it turns sharply to 
the east, and leaves Scotland a little to the north of Aber¬ 
deen : and so rapid is the decline in mean temperature 
to the north of that point, that Shetland only reaches 55. 
It may be noted that we in Perthshire enjoy an average 
summer heat in July of a little over 59, though it 
must be confessed that the temperature of every month 
of July in succession since 1880 has failed to come 
up to the average in our part of Scotland, and in the 
years preceding 1880, the July of 1879 and again of 
1877 were both grievously deficient in summer heat. 
Taking the average of years, however, as our standard, 
we in Perthshire enjoy a mean temperature higher 
than the average touched at any town of the extreme 
north of Scotland during about three months from 
June 15th till September 15th. But to compensate tor 
this, the mean of Perthshire sinks below the mean of Wick 
or Stornoway from about the middle of November, and it 
does not again rise to its level till the beginning of March; 
so that our range of temperature in Perthshire is very con¬ 
siderably greater than that of the northern counties of 
Scotland, being as much as 4J degrees higher than Shet¬ 
land in July, and nearly the same figure in August, but 
fully 2 degrees lower than Shetland or the Hebrides in 
January. But while this is made as a general statement, 
it must be borne in mind that any statement which should 
embrace the whole of Perthshire would be far from simple, 
and would be complicated with many details. Thus the 
winter temperature of Eastern Perthshire is decidedly 
higher than it would otherwise be because of its proximity 
to the German Ocean; and, again, the summer temperature 
of the Carse of Gowrie is lower than it might be but for the 
same cause. In settled calm summer weather, it is no un¬ 
common thing in the course of a journey by railway from 
Dundee to Stirling or the west, to start with a cool breeze 
of east wind, which follows the traveller up the Carse, 
though with continually decreasing force, till near Auch- 
terarder a belt of calm is reached; and a little to the west, 
west winds are met. But the mean temperature of a 
summer afternoon in the Carse of Gowrie, when a cool 
breeze is blowing in from the sea, is very different from 
the mean of some inland districts, even though it should 
be in the uplands, when calm and light airs from the warm 
west blow instead of the bitter east. 
But perhaps a more important and a more interest¬ 
ing feature of the climate of Perthshire is its rainfall, 
in respect of which there is perhaps a greater differ¬ 
ence between the eastern and the western districts of 
the county than there exists between different parts 
of any other county in Scotland. Striking a general 
average, the annual rainfall in those parts of Strath¬ 
more near Perth, and down to the boundary line with 
Forfarshire at Invergowrie, is not much more than one- 
third of the rainfall which descends on the part of the 
county which lies between the County March with Argyll 
in the west round to about the head of Loch Earn in 
the east. The reason of this is not far to seek, for the 
conditions which favour the heaviest rainfall within our 
islands are an elevated tableland with projecting points of 
lofty mountains jutting up above it, as, for instance, in the 
Dartmoor region of the south of England; the Lake dis¬ 
trict in the north-west,—which enjoys the heaviest rain¬ 
fall of our islands;—and a portion of North Wales; and 
these conditions are also met with in the elevated tableland 
which is near the meeting-point of the counties of Argyle, 
Perth, and Stirling. The numerous mountain peaks wring 
out the moisture from the clouds which float over them, 
mostly from the west, and the rain of course falls to lee¬ 
ward, giving Western and part of Central Perthshire an 
abundant supply of rain. But as the clouds drift eastward 
they have all the moisture wrung out of them, and they 
pass over Eastern Perthshire without sending down more 
than slight showers. On the other hand. Eastern Perth¬ 
shire gets its heaviest rains with easterly winds. A good 
example of this occurred in December, 1876, during which 
month a constant series of depressions passed over the 
north of England, giving almost incessant easterly gales, 
with rain or snow; so that the rainfall of that month in 
Eastern Forfarshire and Perthshire was nearly everywhere 
over 10 inches,—the heaviest rainfall of any month in 
these parts within this generation,—but in the usually wet 
West of Scotland it came a long way short of being the 
wettest of months. Or to take a case nearer us in time. 
On last Sunday, the 29th ult., a shallow depression crossed 
over the North of England, and in consequence easterly 
breezes with cold rain were experienced in Scotland, but 
the rain in the east was far heavier than elsewhere. Thus 
Leith had 0.80 of an inch and Dundee 1.08 of an inch, 
while Glasgow had but 0.12 and Ardrossan 0.14 of an inch. 
It thus appears that were it not for the passage of depres¬ 
sions to the south of us, the East of Scotland, and with it 
Eastern Perthshire, would have much less rain than it has; 
