What a mysterious world this Tir-fo-Tuinn, this Land-Under-Wave. How little we know of it, for all that wise men have told us concerning the travelling tides, of currents as mysteriously steadfast in their comings and goings as the comets that from age to age loom briefly upon the stellar roads: how little, though they have put learned designations to a thousand weeds, and given names to ten thousand creatures to whom the whole world of man and all his hopes and dreams are less than a phantom, less than foam. The Gaelic poet who said that the man who goes to Tir-fo-Tuinn goes into another world, where the human soul is sand, and God is but the unloosened salt, tells us as much as the scientist who probes the ocean-mud and reveals dim crustacean life where one had believed to be only a lifeless dark. Above the weed-held palaces of Atlantis, over the soundless bells of Ys, above where Lyonesse is gathered in a foamless oblivion, the plummet may sink and lift a few broken shells, the drag-net may bring to the surface an unknown sea-snail or such a microscopic green Alga as that _Halosphoera viridis_ which science has discovered in the great depths beyond the reach of sunlight: but who can tell, perchance how few who care to know, what Love was, long ago, when there were poets in Lyonesse: what worship was served by white-robed priests among the sunken fanes of Ys: what dreams withstayed and what passions beset the noble and the ignoble in drowned Atlantis, what empires rose and fell there, what gods were lauded and dethroned, and for how long Destiny was patient. Even in the little pools that lie shoreward of the Gardens of the Sea what beauty there is, what obscure life, what fascinating ‘other-world’ association. This piece of kelp is at once _Fucus vesiculosus_ and the long fingers of the Cailliach-Mhara, the Sea-Witch. This great smooth frond is ... I do not know, or forget: but it is the kale of Manan, in sea-groves of which that Shepherd pastures his droves of uncouth sea-swine. This green tracery has a Greek or Latin name, but in legend it is called the Mermaid’s Lace. This little flame-like crest of undulating wrack has a designation longer than itself, but in tales of faerie we know it to be that of which the caps of the pool-elves are fashioned.