Like his use of alliteration, Mahon uses sibilance to convey both sounds and deeper meanings in his poetry. For example:
‘spilling into the skull, marbling the stones’ (‘Day Trip to Donegal’) Here the sounds of the sea in the speaker’s nightmare are echoed in the sibilant ‘s’. The sounds of the line itself remind us of the surging of the sea.
‘shipyard silence’ (‘Ecclesiastes’)
The technique is used here to convey contradiction. A shipyard is supposed to be noisy and busy, yet this one lies empty, a stark symbol of economic and political stagnation.
‘our sky-blue slates are steaming in the sun’ (‘Kinsale’)
Sibilance here conveys brightness and optimism. The smooth, euphonious (pleasant- sounding) combinations of ‘s’ in this line create a buoyant and positive impression of the future, which is juxtaposed with the earlier, heavy ‘d’ sounds of the past.
ASSONANCE
Mahon uses assonance to create rhythm and for its euphony (quality of being pleasing to the ear). For example:
‘a squirming glimmer of gills’ (‘Day Trip to Donegal’)
Here the sharp ‘i’ sounds are quick and light. We imagine the day’s catch all moving on the sunlight. The assonance here causes the line to be
‘abandoned/ to a slow clock of condensation’ (‘A Disused Shed in Co. Wexford’)
The repeated ‘o’ sound both slows the pace of the line and emphasises the stillness and noiselessness of the scene. Additionally, the alliterative ‘c’ sounds remind us of the gentle dripping (or ticking) of the metaphorical clock of condensation.
‘goading his ghost into the howling snow’ (‘Antarctica’)
The long ‘oh’ sounds here create a slow rhythm and remind us of the deliberate, heavy tread of the doomed man as he battles against the blizzard (and his own sense of self-preservation) and trudges off to his doom.