THE IRISH ARAN. 35 
The islands are entirely composed of metamorphosed limestone, 
and the rainfall is excessive from the fact that the islands are the 
first land struck by the westerly winds which have swept over 
the Atlantic, thus becoming saturated with moisture ; the result of 
the excessive rainfall is that the surface of the limestone is 
dissolved away with such rapidity that no spore of moss or other 
green thing can find lodgment for a sufficient time to germinate. 
The barren appearance is intensified by the fact that the numerous 
divisions between the fields consist of loose stone walls like those 
of North Derbyshire. 
On walking over these fields, however, we find that the lime- 
stone is extensively fissured, the fissures running more or less in 
the same direction, and these fissures having been deepened 
by the solvent action of water to the depth of several feet, contain 
an abundant Flora, of course of lime-loving plants. I have 
nowhere seen more luxuriant specimens of many ferns, such as 
the Ceterach, Scolopendrium, Asplenium Ruta-muraria and Tricho- 
manes, Adiantum nigrum and marinum, and last, but not least, 
the true British Maidenhair, Adiantum Capillus-Veneris. Of the 
latter fern, I should think that there are more plants growing 
here than in the remainder of the three kingdoms put together. 
The wind, however, and the cattle between them cut off these 
plants to the level of the surface of the rock, so that no green 
shows at a distance. The only parts that can really be cultivated 
are the slopes, where talus can lodge, and the places which have been 
covered by the drifting sand. _I was quite surprised to see a fine 
crop of grass in a small circular enclosure which had been built on 
_the flat, bare rock, near the beach at the north point of the Great 
Island, and in which a thick layer of sand and seaweed had been 
placed. Excellent potatoes are grown in this sand manured by 
seaweed, as is also the case in the Channel Islands. 
A peculiarity of the stone walls is that no gates or openings are 
left in them, so that when a cow has to be brought from a distant 
field to the road, five or six walls have to be pulled down and 
rebuilt. 
When calcareous rocks are in contact with the sea, it is usual to 
