It was a Romantic death - sublime, poetic and careless. In April 1805, a young man named Charles Gough, a tourist in the Lake District, set out to walk over the forbidding mountain Helvellyn. Even today, walkers on Helvellyn's Striding Ridge are advised to proceed with caution. At the beginning of the 19th century, hill-walking and mountaineering for pleasure were new pursuits. Gough had no specialist clothing or equipment. That day - this was during the Napoleonic wars, in the year of Trafalgar - the local militia were training, so there was no man available to be his guide. He set out alone, except for his dog, probably a spaniel.  Then, nothing. He never arrived in Grasmere. And no one seems to have gone looking. Three months later, a shepherd by the mountain lake Red Tarn came across a little dog barking. Beside her were clothing and a few bones. He ran for help; a crowd came up the mountain. They collected skeletal remains, a few belongings, a hat cut in two, from which it was concluded that Gough had fallen from the precarious ridge and died from head injuries. The dog had not only survived, but had a pup, which didn't make it. A Carlisle newspaper drew the hardheaded conclusion: "The bitch had pupped in a furze near the body of her master, and, shocking to relate, had torn the cloaths from his body and eaten him to a perfect skeleton."  But this carnivorous possibility was not even contemplated by the poets and artists who were to feast for years afterwards on the story of Gough. For them the dog was a hero, who had refused to leave its fallen master's side. The hyperbolic, hysterical and sometimes hilarious permutations of a Romantic legend are wittily surveyed in an exhibition at the Wordsworth Trust in Grasmere, designed by artist Simon Morley, which pursues the story's retellings year by year from 1805 to today.  This is a story that takes us to the heart of Romantic culture. The success of Romanticism as an emotional style that transfigured European social and political history lay precisely in its straddling of the shallow and the deep, the serious and the silly. The legend of Charles Gough and his dog is a wonderful instance of how, in Romanticism, the sublime and the ludicrous are never far apart. It is easy for us to look at all this with what EP Thompson called "the enormous condescension of posterity", but perhaps we would come closer to the creativity of that time if we could so easily find the glorious in the trite, the sonorous in the clanging. It is often said we are the heirs of Romanticism, that the self-inspection and taste for sublime excess of early 19th-century culture is the birth pang of modernity. But the tale of Gough and his dog makes us aware that we are also a long way from that age - that we laugh at things that made Wordsworth cry.  Not that people didn't laugh at Wordsworth's poem "Fidelity" at the time. In the preface to their revolutionary Lyrical Ballads, published in 1798, Wordsworth and Coleridge warned that readers would not find here the florid conventions, the aristocratic affectations, the formality they recognised as literature: "Readers accustomed to the gaudiness and inane phraseology of many modern writers, if they persist in reading this book to its conclusion, will perhaps frequently have to struggle with feelings of strangeness and aukwardness: they will look round for poetry, and will be induced to enquire by what species of courtesy these attempts can be permitted to assume that title."  Nine years later, when Wordsworth published a poem about the death of Gough, reviewers were still sneering at the banality of his poetic voice. His unemphatic telling of the discovery of Gough's body and his loyal dog in "Fidelity" was particularly mocked. One reviewer, who as predicted in the preface to Lyrical Ballads could see no poetry whatsoever in this "poem", made that philistine point by satirically reprinting "Fidelity" as a block of prose. "The language is not only prosaic," said another, "but generally flat, and in some places absolutely mean" - "mean" having definite associations of social inferiority.  "Fidelity" is certainly written in everyday language. The first line flirts with being rubbish: "A barking sound the Shepherd hears." Later he wonders, flatly: "What is the creature doing here?" It is a daring game, which is in even more danger of failing with today's readers; but Wordsworth's genius is to find the sublime in ordinary speech, to release from his sedate cadences bursts of energy that catch the reader by the heart. The poem includes a great - so great you don't notice - evocation of the grandeur of Helvellyn's Red Tarn as an isolated void where echoes create a "symphony austere". Most courageously of all, having established to his own satisfaction the facts of the case - that Gough's dog, far from eating him, maintained a loyal vigil by his side through those months in the mountain solitude - Wordsworth's tale becomes a hymn to nature, to animal souls, a vision of nature as not only sensate but more moral, more infused with love and faith, than denatured and thus dehumanised human beings. The dog was "nourished", he declares, by a hidden power:  How nourished here through such long time He knows, who gave that love sublime, And gave that strength of feeling, great Above all human estimate.  Poetry in early 19th-century Britain had an immediacy now unrecoverable; it was urgent, it was popular, and one of the reasons critics reviled Wordsworth was that the story of Gough and his dog had already been told in verse by the more commercial Walter Scott. In fact, both poems were written in 1805, but Scott's "Helvellyn" was published first, in 1806. Contrast Wordsworth's humble first line with the self-dramatising heroism of Scott's: "I climbed the dark brow of the mighty Helvellyn".  It is Scott who is the myth-maker, drawing up the strands of Gough's tale into a modern martyrdom, inventing a hero of the new love of nature just as Scott's novels mythify Scottish history. For Scott, Gough's death is that of a true nature-lover, and his loyal dog - according to Scott, a terrier - is a fittingly humble mourner. He contrasts this with a feudal lord's death mourned by courtiers, and insists this is the appropriate, meaningful death for a "gentle lover of nature".  Canine fidelity has been extolled since at least the middle ages, but in the Romantic age it became culturally central, with dogs not just attending their owners but taking centre-stage. Later, Queen Victoria would commission portraits of her dogs, beginning in 1836 with a picture of her beloved spaniel Dash.  The man who painted the Queen's dogs was also one of the myth-makers of Gough and his loyal dog. In 1829 Edwin Landseer painted Attachment, inspired by Scott's poem. Landseer's poor little mutt has been rudely displaced from the comforts of the drawing room to a ledge beneath which plummets a terrible abyss; all around are shadowed cliffs and empty air, the remote, inhuman heights of raw nature. And here is the dog, tenderly pawing its prone master, achingly looking into Gough's cold white face. It is a bathetic image of loss in which, somehow, the foolishness of seeing a dog grieve makes it more touching.  If Landseer makes this a sentimental story of grief, the apocalyptic painter Francis Danby brings a Blakeian vision to his picture The Precipice (c1827). The dead climber is a greenish angel cast down from on high, spread out on the rocks, his dog patient at his side.  The story was a gift to Romanticism for so many reasons. A young man of sensibility and artistic aspiration, he was a watercolourist, whose landscapes are picturesque images of Welsh mountain valleys, waterfalls and woods. He was a solitary - no one looked for him when he vanished - and perhaps a melancholic: his possessions found near Red Tarn included a notebook in which he wrote down epitaphs from gravestones in a country churchyard.  And then there is the remarkable behaviour of the dog. The legend of the fidelity of Gough's dog is a critical moment in the emotional history of the British and their pets; it was through the lens of this story that Edinburgh's citizens saw the heroism of Greyfriars Bobby, who guarded his master's tomb for 14 years after the man's death in 1858. This is where Romanticism is the parent of Victorianism; and here, sentiment and sublimity go hand in hand. John Ruskin praised Landseer's The Old Shepherd's Chief Mourner (1837) - the mourner is a dog - as a great modern painting. And if we laugh at Landseer, the same sentimentality becomes awe-inspiring in Turner's watercolour Dawn After the Wreck (c1841). Ruskin described how, from a wreck that killed all hands, "a single dog has come ashore. Utterly exhausted, its limbs failing under it, and sinking into the sand, it stands howling and shivering. The dawn clouds have the first scarlet upon them."  But the richest, and for us the most usable, meaning of this story is also the most difficult to comprehend. It is Wordsworth's transformation of a sad, strange little anecdote into a hymn to nature; his counterfactual declaration that the dog is not simply a hero but the embodiment of natural virtues we human beings have lost. In "Fidelity" he is making a utopian demand: accept the moral grandeur of nature; breathe it, be it, live up to it.  Go for a walk now on Helvellyn and you set out from a car park, on a well-mapped path. The hikers are properly clothed and equipped; you know they will come down without a scratch. No one is silly enough to bring a spaniel. But looking at the majesty of the sun through the woods, the stream tumbling beneath the path, the moss, and the lake of Thirlmere a dark mirror, you begin to understand what Wordsworth, buried in the nearby valley, was on about.  · The Unfortunate Tourist of Helvellyn is at 3 West Gallery @ Island View, The Wordsworth Trust, Dove Cottage, Grasmere, until April 25. Details: 01539 435544. Jonathan Jones is writing a book on Gainsborough's Britain for Granta.
He was a foolish man, hiking on a treacherous mountain alone with his dog. But for Wordsworth and the Romantics, Charles Gough offered a glimpse of the sublime. Jonathan Jones on the making of a myth