This text comes from The Poetical Works of Robert Burns, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Among the heathy hills and ragged woods
The roaring Fyers pours his mossy floods;
Till full he dashes on the rocky mounds,
Where, thro' a shapeless breach, his stream resounds;
As high in air the bursting torrents flow,
As deep recoiling surges foam below,
Prone down the rock the whitening sheet descends,
And viewless Echo's ear, astonished, rends.
Dim-seen, thro' rising mists, and ceaseless show'rs,
The hoary cavern, wide-surrounding, low'rs.
Still, thro' the gap the struggling river toils,
And still, below, the horrid cauldron boils—
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