220 THE CLIMATE OF THE NORTH COAST OF WALES 
Yet Llyn Dulyn is only fourteen miles in a straight line from 
Colwyn Bay, and Pen-y-gwryd about six miles further to the 
south-west. The explanation of this phenomenon has long been 
known. It is that the warm south-west winds, laden with 
moisture from the Atlantic, strike the mountains of North Wales, 
and are forced by these to rise into a colder region of the 
atmosphere. Now “the capacity of air for containing moisture 
doubles for a rise of temperature from 0° to 16°, from 16° to 
33°, from 33° to 52°, from 52° to 738°, and from 73° to 96°.” 
(Hygrometrical Tables by Jas. GLAISHER, PRS. ) It follows from 
this, that air from the Atlantic reaching Snowdon at a tempera- 
ture of 52°, and being cooled down to 33°, would have to part 
with one-half its moisture in the form of rain, and passing on to 
the north coast, will arrive there comparatively dry. 
There is a feature in the climate of the coast of Flintshire and 
Denbighshire, west of the mouth of the Dee, that deserves 
notice, as it adds greatly to its value as a winter residence. 
Those who are much in the habit of travelling westward along 
the Holyhead line in winter, cannot fail to have observed that, 
in foggy weather, the fog suddenly diminishes in thickness, if it 
does not altogether disappear, at a point between Mostyn and 
Prestatyn somewhere about the Point of Ayr, where the Estuary 
of the Dee ends. From this point to Llandudno at all events, 
and probably all along the north Coast of Anglesey, fogs of any 
density are of rare occurrence. | have not attempted to collate 
the returns in GLAIsHER’s Reports on this subject, because such 
returns, depending as they do merely on the impression in the 
mind of the reporter, are of little value. But the fact is 
undeniable, and is the more remarkable, as the Jrish Channel 
between Holyhead and Kingstown has a bad reputation for fogs. 
As an illustration, I may quote an entry in my diary on 
February 20th, 1891, when I travelled to London. ‘“ Misty or 
foggy everywhere. West of Point of Ayr one could see the hills 
four or five miles off—east of it about 400 or 500 yards.” The 
cause of this immunity from thick fog has yet to be ascertained. 
Possibly it may be due (paradoxical as it may seem) to the 
comparative moisture of the atmosphere of the coast, as compared 
with that further inland. For it is certain that evaporation from 
the earth is greater at equal temperatures in proportion as the 
air is drier, and that evaporation causes cooling of the surface. 
It seems, therefore, probable that this cooling of the earth may 
condense the aqueous vapour in the lower strata of the atmosphere 
into fog in the drier region; while in the moistcr, the comparatively 
slow evaporation leaves it uncondensed and the air consequently 
clear. This, however, is only true within certain somewhat 
narrow limits of temperature and humidity. 
Another obscure question is -What constitutes a bracing 
climate? According to my view, a dry climate is the really 
bracing one. But this implies, as we have seen, a climate of at 
