206 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
Hay. In the papers on the teeth of vertebrate animals read 
by Mr James Stewart at the beginning of the session, the 
peculiarities of the cutting teeth of rodents were pointed 
out, especially the way in which the upper and lower teeth 
work against each other, and are thus kept a proper length. 
In the specimen exhibited, the result of a want of apposi¬ 
tion in the teeth was well shown. Some accident having 
happened to the lower right jaw, the teeth (with the ex¬ 
ception of the lower right incisor) had continued to grow 
till they attained an inordinate length, and, in the case of 
the upper ones, had almost formed rings, while the in¬ 
jured jaw had become much diseased. The result to 
the unfortunate animal was that what little food it could 
partake of must have been sucked in, as there was no 
possibility of its using its teeth. The specimen afforded 
a good illustration of the character of rodent incisor teeth, 
namely, that during the life of the animal they continue to 
grow at the root end, and to be worn away at the free end. 
The latter, being softer on the inner side than it is on the 
outer, has thus a chisel-like edge always kept ready for use. 
The following papers were read 
1. “ The Climate of the British Islands, with special lefer- 
ence to Perthshire.’’ By the Rev. A. Campbell, 
Errol. 
The peculiarities of the climate of the British Islands 
are due to a very great extent to their geographical 
position. To the eastward of us we have the Continent 
of Europe, where, as a general rule, the barometer is 
high in the winter and low in the summer months; 
and to the west of us there is the Atlantic Ocean, where 
the barometer is low in the winter and high in the 
summer. It is to the fact that we lie between these two 
areas of differing pressure, that we owe the many and 
rapid changes which occur in our climate, and that we 
find it so difficult to forecast the weather for more than a 
single day. 
The shape of the British Islands has also not a little 
to do with the climate. The winter temperature of Scot¬ 
land, especially in the northern counties, is greatly modi¬ 
fied by the fact that it is everywhere in close contact with 
the ocean ; and as a consequence, the average January 
temperature of Sumburgh Head or Stornoway is equal to 
the average temperature of the same month at Yarmouth 
or London. In the present year, indeed, the figures for 
January show results for the north of Scotland, as com¬ 
pared with the south of England, remarkably favour¬ 
able to the north, so far as temperature is concerned. At 
Sumburgh Head the mean of the maximum temperatures 
of January this year was 42T, and the mean of the minima 
was 34'4. At Stornoway the mean maximum figure was 
precisely the same as at Sumburgh Head, and the mean 
minimum of the month was 34'7. Now, contrasting these 
figures with those which apply to a few of the stations in 
the south of England, the difference is very marked. 
Thus in London the mean of the maxima in January last 
was 41 - 3, and the mean of the minimum 32'5; and at 
Cambridge the figures were lower still—39'8 the mean of 
the maximum and 29‘7 the mean of the minimum ; and 
even at Hurst Castle, which is in the extreme south of 
Hampshire, just opposite the west end of the Isle of 
Wight, the mean of the maxima of January was 40'3, or 
nearly a degree lower than Stornoway, and the mean of the 
minima was 34T, or half-a-degree lower than Stornoway. 
But it must be remarked, that the deficiency of heat in 
January of this year has been much more marked in the 
south of England than in Scotland; for while the minimum 
of January is below the average minimum of that month 
by 3'4 degrees at Hurst Castle and 3'9 at Scilly, Storno¬ 
way was 0'5 above the average in its minimum. January 
was therefore a good deal below the average in the ex¬ 
treme south, but not colder than the average in the far 
north. 
But if the isothermal lines stretch north and south 
in January, they do not long continue in this abnormal 
condition. In February there is a decided recovery of 
temperature in the south, while in the north, especially 
in those places which are in contact with the sea, the 
temperature is about stationary at its lowest point ; 
and in the month of February this year, the difference 
between the temperature in the north and south is in¬ 
tensified by the fact that in England, especially in the 
southern counties, February was much warmer than the 
average, London and Oxford being both 3'4 above the 
mean, while Stornoway and Wick were 1‘7 and 1‘5 
below the mean. In February of this year, therefore, 
the isothermal lines took the form which they usually 
assume in March, and stretched across our islands nearly 
from east to west. But this divergence from the ordinary 
rule was again rectified in March, when the temperature, 
below the average everywhere, was especially low in the 
south, and the mean of the minima at Cambridge was 2‘9 
degrees lower than the mean of the minima at Wick. 
In the summer months, our insular position, and the 
facility with which the ocean breezes get access to all 
our stations, not only reduces the mean temperature 
of July and August everywhere within our islands, but 
makes the Scotch mean summer temperature very much 
