THE CLIMATE OF THE NORTH COAST OF WALES. 219 
has the advantage of being about 170 miles further south; yet 
the winters are milder at Llandudno than at Brighton. Further, 
the sea on the north coast of Wales is so shallow that it cools 
down rapidly nnder the influence of severe weather. On January 
12th of this year I found the temperature of the sea bottom 
some five fathoms below the surface to be 36°-5, when the 
temperature of the air was 49°. On January 11th, 1890, the 
temperature at the same depth, taken in the same manner with 
the same thermometer, was 46°, showing how greatly the sea 
temperature at shallow depths varies according to the atmos- 
pheric conditions. We had had some cold weather from 
January 5th to 11th, 1891, while the early part of January, 1890, 
was remarkably mild. On the whole I am inclined to think that 
the comparatively large amount of moisture in the atmosphere 
acting as a check both to the radiation of the sun’s heat /o the 
earth, and of the heat absorbed during the day from the earth 
at night, has at least as much to do with the equable climate of 
this coast as the “Gulf Stream.” Tynpaut has shown what an 
enormous power of checking radiation is possessed by Aqueous 
Vapour (Heat as a Mode of Motion, page 403.) The consequence 
is that while the Isothermal lines in this country run north and 
south in winter, they run about east and west in summer. In 
other words, the mean temperature of Colwyn Bay or Llandudno 
is about the same as the Isle of Wight in January, and as 
Newcastle-on-Tyne in July. 
The rainfall on the North Wales coast as represented by 
Colwyn Bay, may be considered as a moderate one. Compared 
with the London neighbourhood (Blackheath) an average of ten 
years (see Table III.) gives 30:77 inches for the former, against 
93-36 inches for the latter. Taking the months in their order of 
wetness, (see Table IV.) we find that in both places October and 
November are wet months. But while at Blackheath July heads 
the list with 2°58 inches, at Colwyn Bay it comes sixth with only 
2°49 inches; and June, which is fifth at Blackheath with 1:96 
inches, is last (7.c., driest) but one at Colwyn Bay with 1:89 inches. 
These are the only two months in which the rainfall is actually 
less at Colwyn Bay than London. August, which is the wettest 
month at Colwyn after November, exceeds Blackheath by 1°40 
inches, this being the largest difference in any month. 
Comparing Colwyn Bay with Chester, I find that on an 
average of eleven years (1878 and 1888 inclusive) the former 
place shows a rainfall of 31°11 inches on 176 days in the year, 
while Chester averages 27°92 inches on 182 days. But if we 
compare Colwyn Bay with the mountainous region to the south- 
west, we see a remarkable difference. Taking the rainfall of 
1890 as an example, we have— 
Colwyn Bay .. il. as .. 81:10 inches 
Llyn Dulyn, 1622 ft. above sea... 124°40__,, 
Pen-y-gwryd, 880 ft 34 1.218680 55 
G 
