The London fog, caused by the smoke of thousands of coal fires, domestic and industrial, is a familiar feature in both historical fiction and fiction written before the Clean Air Act of 1956.
Adding fog is an easy way for a writer to create a mood of foreboding and danger. It’s an essential part of the scene in late Victorian London:
'The yellow glare from the shop-windows streamed out into the steamy, vaporous air, and threw a murky, shifting radiance across the crowded thoroughfare. There was, to my mind, something eerie and ghost-like in the endless procession of faces which flitted across these narrow bars of light.’
'...Ships, towers, domes, theatres, and temples lie
Open unto the fields, and to the sky;
All bright and glittering in the smokeless air…'
So said Wordsworth in September 1802. Could the air really have been as clear as he suggests?
Pugin and Rowlandson's illustration, just a few years later, shows a definite haze hanging over the east of the City, beyond St Paul‘s. (The bridge shown is Blackfriars.)
John Evelyn’s Fumifugium, published in 1661, describes a heavily polluted city:
‘The City of London resembles the face rather of Mount Ætna, the Court of Vulcan, Stromboli, or the Suburbs of Hell, than an Assembly of Rational Creatures, and the imperial seat of our incomparable Monarch. For when in all other places the Aer is most Serene and Pure, it is here Ecclipsed with such a Cloud of Sulphure, as the Sun itself, which gives day to all the World besides, is hardly able to penetrate and impart it here; and the weary Traveller, at many Miles distance, sooner smells, than sees the City to which he repairs.’
It’s suggested that there was an element of political allegory in Evelyn’s writing. Should it be taken literally? Probably. Wordsworth is the odd one out. While the air may indeed have been unusually clear that morning in September 1802, the sight he saw was probably not typical.