MOST people will have heard the urban legend of the man who built a car engine to "crack" water into its elemental components of hydrogen and oxygen back in the 1960s.
He allegedly devised a means of setting fire to the hydrogen under great pressure, and fanning the flame with the oxygen.
He discovered that the only waste product was ... water.
He took the blueprint for this engine to Shell or BP.
They said this would revolutionise the internal combustion engine and bought the plan and patent from him for £2m.
That, of course, was the last anybody heard of it.
I stumbled across a news item the Examiner published in December 1941 that had the same kind of intrigue.
It concerned a former Huddersfield man who claimed he had invented a device that could cut a petrol engine's consumption by half.
"A car fitted with the invention has to be started on petrol," said Mr John Edward Iredale Dyson, a civil servant and part-time electrical engineer who moved from Huddersfield to St Annes in 1922.
"But once it is in motion it will run on air with just a small amount of petrol."
Mr Dyson had shown a passion for motor cars since their earliest days.
He owned one of the first cars in Huddersfield, a 4.5hp De Dion, registration number CX 34, and had actually hill-climbed it in May 1907, winning a Yorkshire Automobile Club gold medal.
The petrol-saving device was clearly the result of many hours' tinkering between then and 1941.
Remember this was in wartime Britain, when petrol was in short supply.
Not unnaturally, Mr Dyson, a former civil servant, was mowed under by orders for the device.
"I can make two a week in my spare time," he said. "But so many people have a need for it in these days of petrol rationing that I cannot possibly make enough."
I am not mechanically-minded, so I'm obliged to quote verbatim from the Examiner report which described the device and its function.
"The invention is concerned with attachments to internal combustion engines providing for the supply to the carburettor ... of vapour generated from naphthalene contained in a receptacle adjoining the cylinder head and exhaust pipe ..."
Naphthalene is a coal tar derivative, the active ingredient in mothballs, so Mr Dyson had invented not only a petrol saver but also a travelling insecticide and de-wormer.
He seems not to have explored this side of the equation, but was aware that his invention could have patriotic and military applications.
"This gadget would surely help the nation a great deal at the present time if it could be fitted to tanks or aeroplanes.
"It is often said that the country with the most tanks or planes will win the war, but these machines are useless without petrol and therefore the saving of fuel is as important as the making of machines."
Faultless logic - but there is no evidence that the War Office took up his offer, nor that the device was adopted for civilian use when the war was over.
Did Mr Dyson's device go the way of the water-cracking engine?
We may never know.