'If electricity had an odour...'

It was inevitable that John Betjeman, the bard of the Metropolitan line, would make an appearance in Peter Ackroyd's London Under, and so he does. Ackroyd, writing about the distinctive smell of the London Underground – 'a faintly sour, faintly singed odour. It resembles the smell of hair cut with electric blades. There is also the taint of dust, largely comprised of human skin. If electricity had an odour, it would be this' – notes that Betjeman, in his verse autobiography Summoned by Bells, recalled that, in the Twenties, the Central line 'had the odour of ozone; but it was not a natural smell emanating from the sea or from the seaweed. It was not of the ocean...'
  Indeed it wasn't. Here's the passage, part of a description of happy days spent riding the Underground for hours on end with a young friend:

'We knew the different railways by their smells.
The City and South reeked like a changing-room;
Its orange engines and old rolling stock,
Its narrow platforms, undulating tracks,
Seemed even then historic. Next in age,
The Central London, with its cut-glass shades
On draughty stations, had an ozone smell –
Not seaweed-scented ozone from the sea
But something chemical from Birmingham.'

  Betjeman was remembering an experiment conducted by the Central London line in 1918 when it was decided to freshen the air by pumping a version of the invigorating seaside smell of 'ozone' into the stations. The effect, unfortunately, was to make passengers feel faintly nauseous – sea sick, perhaps?
  The tang of 'ozone' in sea air was greatly relished by visitors to the seaside from the smoky towns of coal-fired England. However, science now tells us that the smell we still refer to as 'ozone' is in fact that of a compound called Dimethyl Sulphide, which in combination with other chemicals present in sea air produces the distinctive bracing fragrance of the seaside. Aah, just smell that Dimethyl Sulphide – makes you glad to be alive... No, it will never catch on.
  (Incidentally, the dust in the Underground is not largely composed of skin particles. More of it consists of tiny metal fragments thrown up by the trains, especially when they're braking. And of course those 'cut-glass shades' on Central Line stations are long gone, more's the pity.)