For many years, if you looked over to your right as your train rattled into Glasgow Central from the south, you would see - among the rooftops and battlements of the city's East End marketplace The Barras - a cluster of signs. Hand-painted and home-made, these signs informed visitors to Glasgow of the identities of several key Scots: 'William Wallace - Warrior', read one. Another of the fabled signs showed how fierce patriotism had overcome any inhibitions in the spelling department. It read, 'John Logie Baird - Inventor'!

Sadly these improvised billboards are long gone now, but the pride the Scots take in their country's contribution to the sciences and technology is still very much alive. And rightly so, for few nations of Scotland's size can lay claim to having made such a mammoth impact on the world we live in. To understand the true extent of this contribution we need only look at the overlapping lives of four extraordinary Scotsmen, who helped to create the global communications network that we take for granted today.

The founding father of modern physics, was born William Thompson in Belfast, in 1824, but the family relocated to Glasgow when he was just nine years old and the city would become his home. An extraordinary academic career followed. At the age of fifteen Thompson won the Glasgow University class prize in astronomy. By the time he was seventeen Thompson had already published several essays in the academic journals, formulating theories that would later be described as 'some of the most valuable, science-forming ideas.'

In 1841 he left Glasgow for Peterhouse College Cambridge, where he shone so brightly in his finals that one examiner is reported to have told another that 'you and I are just about to fit to mend his pens!' In 1846, the year after graduation, he was appointed Professor of Natural Philosophy at Glasgow University. He was just twenty-two years old. Over the next ten years Thompson's work in physics would help redefine the discipline and bring him academic glory. His move into the public eye, into fame and wealth, would come with his incredible second career...

At the height of the Victorian era there really was only one career for an ambitious man to have. The engineer was the most lauded position of the age and men like Brunel and Stephenson were the rock stars of their day, propelling the world towards the twentieth century and garnering adulation and riches along the way.

For several years the Atlantic Telegraph Company had been formulating plans to lay a trans-Atlantic telegraph cable. In charge of the project was ATCs chief engineer William Wildman. Thompson was asked to join the project purely as a 'scientific advisor'. From the outset he had misgivings about the design of the cable and clashed repeatedly with Wildman, who regarded Thompson as a boffin and a backroom boy more at home with lab experiments than the practicalities of laying thousands of miles of undersea cable.

In an era filled with fraught and difficult engineering projects this was to be one of the most challenging. In August 1857 Thompson sailed on board the cable-laying ship HMS Agamemnon. This attempt was abandoned when the cable snapped. Another attempt was made the following summer, but the ship was forced to turn back because of terrible storms. In August 1858 the cable was finally laid. To everyone's surprise except Thompson's it failed and was then completely destroyed when Wildman ran a charge of 2000 volts through it. Thompson took over the project. He was no longer a green 'backroom boy'. He had gained real hands-on engineering experience, was unafraid to get his hands dirty in an on-ship crisis and was well respected by his fellow team members. In 1865 he made a third attempt at laying the trans-Atlantic cable. It too snapped after 1,200 miles had been laid.

The Atlantic Telegraph Company were ready to abandon the project as unworkable. Thompson convinced them it could be done and in August 1866, eleven years after he was hired, he was proved right when the first trans-Atlantic telegraph cable was successfully laid, changing global communications forever. Thompson was knighted the same year.

On March 7th 1876, less than a decade after William Thompson became the First Baron Kelvin, the US patent office issued Patent No 174,465 to another young Scots inventor. The patent covered the method of and apparatus for, transmitting vocal and other sounds telegraphically. The apparatus was the telephone and its inventor Alexander Graham Bell (who was still in his twenties) would ultimately take the fundamentals laid down by Thompson to levels even Thompson had never envisaged.

Born (he adopted the Graham out of affection for a family friend) in Edinburgh in 1847 - the same year Thompson was taking up his professorship at Glasgow University - Bell developed his interest in acoustics and sound transmission in part through attempts to communicate with his deaf mother. Bell's name will, of course, be forever intertwined with the telephone, but consider for a moment the other inventions he had a hand in. Photophone transmission (a device enabling the transmission of sound on a beam of light) was a direct antecedent of today's fibre-optic systems. Bell then experimented with magnetic fields for reproducing sound, which is the basic principle behind today's tape recorders, hard drives and floppy discs. He installed a rudimentary air-conditioning system in his home, a century before they became commonplace. Add to this the metal detector, the hydrofoil and solar panels. At the time of his death in 1922 Bell had registered sole patents on 18 inventions, as well as 12 shared patents with other collaborators. He was awarded the Edison Medal for 'meritorious achievement in the invention of the telephone' in 1914.

That same year another young Scotsman was engaged in an experiment that would have spectacular results. was trying to see if he could create diamonds by heating graphite. He succeeded in shorting out the electrical supply for the whole of Glasgow!

Baird was born in Helensburgh in 1888 (the same year that Bell became one of the founding fathers of America's National Geographic Society) and had his studies at Glasgow University interrupted by the First World War. He never resumed them. A driven man, his early years were marked by frustration. In addition to depriving Glasgow of electricity, he invented a glass razor. It was completely rust-proof, but not, alas, shatter-proof. Inspired by car-tyres he invented pneumatic shoes. They had a tendency to explode. The invention Baird persevered with, the television, would, like the work of Thompson and Bell before him, change the world forever.

It was not to be an easy ride. Baird's ideas were so far ahead of their time that he had difficulty getting people to take him seriously. The night before Halloween 1925, in his London laboratory, he succeeded in broadcasting the worlds first real television picture of a moving shot of a ventriloquists dummy. Excited and hungry for publicity, he charged down to Fleet Street, to the offices of , where he tried to accost the news editor with his story. 'For God's sake', the editor is reported to have said to his staff, 'go down to reception and get rid of this lunatic. He says he's got a machine for seeing by wireless! Watch him - he may have a razor on him!'

Baird would prove his sanity to and to the world, less than two years later when, in 1927, he transmitted a live television signal between London and Glasgow. The signal travelled over 400 miles through a telephone line, the kind of cable developed by Bell and Thompson before him.

That same year, 1927, a thirty-eight-year-old Scotsman became the first Director-General of a new company which was to embrace Baird's invention and use it to help shape the world for generations to come. The Scotsman was and the company he headed was the British Broadcasting Corporation.

Reith was born in Stonehaven in 1889. He was, by all accounts an indolent child who would have been perfectly happy to drift through life dabbling in further education. A late-bloomer Reith tried his hand at engineering, soldiering and politics before joining the embryonic British Broadcasting Company (not Corporation) in 1922 (the same year, coincidentally, that Graham Bell passed away). He was immediately, in his own words, 'confronted with problems of which I had no experience: copyright and performing rights, Marconi patents, associations of concert artists, authors, playwrights, composers, publishers, theatre managers, wireless manufacturers . . . '

But Reith like his predecessors was a pragmatist and a fast learner. He soon boiled the issues facing him down into what became famous as the 'Reithian directive', that the BBC's primary goal was to 'inform, educate and entertain'. It is a directive that even now, eighty years later, underpins the work of the BBC.

What about new communications technology in Scotland today? Glasgow was named the 'world's most intelligent community', in 2004 by a New York-based think tank because of the city's energy in rolling out new broadband networks to connect its businesses and people with the global community.

What would these four Scots have thought of our communications today? Consider the world they entered and the one they left behind them. When William Thompson was born in 1824 there were no motor cars or electrical lighting. Men still crossed the Atlantic in creaking wooden ships and Beethovens 9th Symphony was performed for the first time! When John Reith died in 1971, less than a century and a half later, the first manned space station was in orbit, astronauts were driving across the surface of the moon in the Lunar Rover and Led Zeppelin released their landmark fourth album. Meanwhile, in a small office in BBN Technologies, in Cambridge USA, Ray Tomlinson pressed the return key on his computer, sent the first ever email and thus shepherded us into an era of communication unlike any the world had ever seen, but one undeniably built on the foundations laid by Thompson, Bell, Baird and Reith.

Perhaps its about time to look at restoring those hand-painted signs over the Barras...

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