Of many a thorny shire tell you notes,
Some let me make you of the water's speeches.
Behind a pot of ferns the wagging clock
Tells me the hour's word, the neural meaning
Flies on the shafted disk, declaims the morning
And tells the windy weather in the cock.
Some let me make you of the meadow's signs;
The signal grass that tells me all I know
Breaks with the wormy winter through the eye.
Some let me tell you of the raven's sins.
Especially when the October wind
(Some let me make you of autumnal spells,
The spider-tongued, and the loud hill of Wales)
With fists of turnips punishes the land,
Some let me make you of the heartless words.
The heart is drained that, spelling in the scurry
I have no idea what this means. This, again, may be the point. 
 The rationalistic explanation is that the ‘spider-tongued’ (a substantive plural, as in ‘(those) who have tongues like spiders’) are the poets who “weave” words together to make ‘spells’. (This is the etymology of ‘rhapsody’, which Thomas was, as an adorer of words, inclined to know). 
 ‘loud’ is yet another adjective used to give a regularly unspeaking thing, like a hill or a tree, a voice. A hill is the most ‘loud’ when the wind (maybe the harsh October wind?) runs over it.
Especially when the October wind