At the lowest point in William's Smith's life in 1819 he jumped in a stagecoach in London and ended up in Northallerton. It was probably the best move he ever made. Smith was a self-made man, the eldest son of a country blacksmith in Oxfordshire, who was born with extraordinary talents. As a boy, Smith had a fascination with the rocks and the fossils which could be found locally.

He had little formal schooling but one of his many practical talents was the ability to sell himself. At the age of 18 he landed a job as a surveyor building a canal in Somerset.

As the navvies gouged out the waterway, Smith absorbed himself in the layers of strata that the picks and shovels were revealing in cross section. The science of geology was in its infancy and in those days it tended to be the province of gifted scientific amateurs who had sufficient private means to pursue their hobby.

Smith, humbly-born, possessed something better than money. His job gave him unique access to the material being studied and he had enormous ambition.

No sooner had his promising employment began than it abruptly ended. For reasons not entirely clear, Smith was dismissed from his canal-building job. For the remainder of his working life he was a freelance surveyor, travelling all over the country.

By all accounts "Strata" Smith was a man who was easy to get on with. Coal miners passed to him their underground knowledge on how to interpret the presence of workable seams by the rock formations. Smith came to the conclusion that sedimentary rocks could be identified by the fossils they contained, and that these rocks were always arranged in the same order. As he worked his way around the country, he saw that the strata revealed by the Somerset canal navvies were repeated in other areas and some outcrops stretched right across the country.

There's a story that Smith was in York when he first formulated his notion of "fossil-ordered stratigraphy" and that he climbed to the top of the Minster tower to declaim it.

In 1799, he brought together his surveyor's skills and his scientific observations to create a geological map of the area around Bath. By 1815 he was ready for something more ambitious – a great work which would be the culmination of his prodigious researches. It was called A Delineation of the Strata of England and Wales with part of Scotland; exhibiting the collieries and mines, the marshes and fen lands originally overflowed by the sea, and the Varieties of Soil according to the variations in the Substrata, illustrated by the most Descriptive Names by W Smith

A more eye-catching title given to it in recent times in a best-selling book was The Map that Changed the World.

The scale of the original map was five miles to the inch and it would have been eight feet long by six feet wide if it had ever appeared as one sheet. It was published in 15 sections, each folded into six panels and scientifically it was earth-shaking. Commercially, its practical value was immense. It made men's fortunes by identifying where to dig for the minerals that would fuel the Industrial Revolution.

Yet Smith, an original thinker and supreme in his field, was neglected. The financial backing he expected did not happen. Geology remained the province of gentlemen and many looked down their noses at this man from a more modest background. When they founded the Geological Society, Smith, the foremost geologist, was not invited to join. He was bitterly upset and the snub rankled with him for many years.

Cold-shouldered by his peers, Smith found things running out of control in his career and in his private life. His wife Mary Ann was hard to cope with. She suffered from chronic mental health problems and was in and out of hospital. From hospital records she seems to have suffered from a sort of nymphomania.

Smith's original maps which had taken years of fieldwork were plagiarised by lesser men who tried to take the credit for his insights. He fell behind on the mortgage of a house and ran up bills
for London accommodation he could not afford.

When the bailiffs caught up with him he was arrested and thrown into one of London's notorious debtors' jails, called King's Bench, for several weeks.

On August 31, 1819 Smith, now homeless, was released from prison and on the same day made the fateful stagecoach journey to Yorkshire – where his fortunes, at last, were to improve.

He and his wife climbed down from the coach in Northallerton looking for work and a place to live. The following year, the Corporation at Scarborough asked him if he could sort out their water supply. Smith was immediately impressed by what he found on the coast. According to a journal kept by Smith's nephew John Phillips, "he came to this romantic and delightful town in the hope of soothing the mental aberration of his wife, which became very manifest in this year." According to Phillips (who Smith brought up and became the professor of Geology at Oxford), Mary Ann was "a mad, bad wife" who was completely unsuited to be the consort of a man of scientific and thoughtful disposition.

Scarborough seems to have had an immediately cheering effect on Smith himself. He wrote approvingly: "Everyone here is very fond of talking of geology." It was an enthusiasm which the rest of Yorkshire seems to have shared because he was able to put his difficult finances on a firmer footing by lecturing on the subject in York, Leeds, Hull and Sheffield.

More importantly, his presence was noted by an amateur geologist who was only too willing to get the immense scientific contribution which Smith had made recognised.

Sir John Johnstone of Hackness Hall was a geology buff, a man of influence in the world of science and the local MP. He hired Smith as his land steward and gave him the use of a nearby vicarage. When the idea came up for a museum in Scarborough, Smith helped devise a radical plan. It would be built in the Doric style, 50 feet high and 40 feet in diameter with a spiral staircase up the middle. The fossils would be arranged around the sides in such a way as to make strikingly clear to a visitor how layers of rock were laid down in actuality. The youngest rock and fossils were at the top and the oldest strata at the bottom.

Sir John Johnstone provided the stone free from his Hackness estate. But the cost was still £1,500, quite a lot for a small town. They managed to raise £1,000 and borrowed the rest – a debt which was to remain pretty much unchanged for the rest of the museum's independent life.

The Rotunda was opened in 1829 as one of the country's first purpose-built museums. For the members of Scarborough Philosophical Society, practical men interested in the application of geology, it was a
wonderful showcase.

But as the Victorian period moved on, so did scientific tastes. Enthusiasm switched from dead rocks to livelier ethnography. The museum's job was now to be a window on the world. It became stuffed with exhibits provided by the many retired sea captains in the town who donated their exotic bits and pieces brought back from exotic shores.

In the 20th century, local interest dwindled further. In 1937, the philosophical society folded and the council took over the Rotunda. On the exterior, the stone became badly weathered through being so close to the seafront. Inside, things were no better. The place had all become rather sad by the time Simon Winchester came to write his book, The Map That Changed the World published seven years ago. Having visited the Rotunda, Winchester demolished it in a couple of scathing sentences. "In recent years the building has become a tawdry and half-forgotten structure....full of junky memorabilia."

But two years ago, with the aid of European and Heritage Lottery Fund cash, the council embarked on a facelift that would return the Rotunda to its origins and honour Smith's name.

A lift has now been installed up the middle and stepping out from it under that great dome is a magical experience. There's also a handsome new "Geology Now" gallery and a "Gateway to the Dinosaur Coast" section on the ground floor where children especially can
have fun.

Karen Snowden, the head of collections at Scarborough, says of the £4.4m restoration of the Grade II-starred listed building: "This was the lively end of Scarborough in its heyday as a spa. The Rotunda was built on the main carriage route to the sands – so all the posh people came past your front door."

In the beginning they paid one shilling a head. Later, in more democratic times, they aimed for a broader audience. Admission came down to threepence and a deal was done with the Bass brewery to allow employees who came by the trainload on day trips in for free.

Today they have a reproduction of the Map That Changed the World at the Rotunda. The original is in the place that for so long spurned its maker – the headquarters of the Geological Society
at Burlington House in Piccadilly
in London.

It was only in 1832, towards the end of Smith's life, that the society softened in their attitude towards the self-taught original thinker they had preferred to overlook. Prompted partly by Sir John Johnstone, the society awarded Smith their highest honour, the Wollaston Medal and he also received a government pension of £100 a year.

The new-look Rotunda now bears the name of the man who was once so neglected he believed he would die forgotten in the poorhouse. In a
final irony, the re-opening ceremony next Friday is being performed by
Lord Oxburgh, current president of the Geological Society.