London fogs – then and now


  • L. C. W. Bonacina

This article was previously published asBonacina (1950).

Though London's smoke-pall continues to vitiate the sunlight of winter and though atmospheric pollution records do not appear to favour the metropolis in comparison with the more palpably smoky towns in the Midlands and North of England, there has been a vast improvement in the character of smoke fogs and hazes during the last thirty or forty years. In fact brown pea-soup “London Particulars” in the Victorian sense are things of the past; and as a late Victorian born in 1882 with lively memories of the eighteen-nineties and nineteen-hundreds I should like to say something about this improvement which is certainly not appreciated by the younger meteorologists and others.

To begin with let us remember that, by the commencement of the nineteenth century, the capital had grown sufficiently big for its smoke problem to become serious, but that by the end of the century it was still sufficiently small and badly drained to allow the dense Thames Valley water-fogs to drift into the central parts, there to be reinforced by local radiation and to become blackened and thickened by smoke from the chimneys. In 1835, two years before the accession of Queen Victoria, Wordsworth in a minor poem recalls having gazed forth from “Hampstead's breezy heath” on London's “black wreath” which, if less extensive than it is today, was probably a good deal more concentrated and poisonous. The great poet, indeed, in company with a brother poet, the Reverend Thomas Crabbe, was gazing upon an evil thing which through-out the Queen's long reign was to make its own contribution to the still swollen death-rates of an age which lacked our twentieth century hygiene, sanitation, medicine and social amenities.

A really bad nineteenth century fog appeared early in the morning as a thick white mist, like country fog, only dirtier. With the lighting of the fires it would soon become yellow and pungent, irritating the throat and eyes, till by midday the continued outpouring of chimney products would have turned the fog a sooty brownish black causing the darkness of night. During the afternoon there might be a partial improvement to the lighter yellow phase, but following the early sunset with renewed condensation through radiation the density of the fog would be such as to bring all street traffic to a standstill. Then hansom cabs and other vehicles might find themselves on the footways, and in the general chaos one heard a good deal of good-humoured Cockney banter interspersed with more caustic jibes. A pedestrian could easily spend the evening looking for his house round the corner, and when he did get home would find the rooms half filled with the choking fog.

It would sometimes happen, too, during the last century that, with no ground fog at all and normal surface visibility, the darkness of night came down upon the city about 10 or 11a.m. and persisted till it became indistinguishable from nightfall about 4p.m. These “overhead fogs”, or smoke hazes (much less frequent to-day in consequence of smoke abatement), were occasioned by the presence of a sheet of low stratus checking surface condensation but keeping the smoke down by the well-known “lid” effect of a temperature inversion. The artistic impressionist certainly revelled in this sort of “day” especially if the murky pall partially lifted so as to reveal St. Paul's Cathedral and Westminster Abbey picturesquely silhouetted in strange tawny shades. On occasions like those when the natural sunlight could not get through, London, so far from looking the noble capital of England's green and pleasant land, seemed a hideous monster “City of Dreadful Night” bereft of its very geographical location. Obsessed with this idea I would sometimes slink away to one or other of the great railway termini with no more practical purpose than to see the hansoms lined up for the arrival of a long-distance express, and so reassure myself that there really were limits to the be-sooted city, beyond which lay the fair rural shires and all the beauty of the woods and hills. I recall, too, how utterly gruesome it was on such days of Stygian gloom to see the Victorian funerals, with their plumed black steeds and craped mutes, stalking through the dismal streets.

Seasonal variations

Fortunately fogs, even during the worst decades of the later nineteenth century, were only occasional incidents in the ordinary course of winter weather, though they were a persistently recurrent scourge in the quieter winters of anticyclonic type. In those days, as in these, the typical London fog was strictly conditioned by the absence of wind and cloud, and I have known thick fogs in the swift sequences of mid-winter weather to be succeeded by heavy rain or snow with a gale all within twelve hours. Fogs lasting all day were always confined to the period of low sun – November, December, January and early February – though widespread dense fog was common enough by night in October, and not very uncommon in March. During the summer months major fogs were virtually unknown in the nineteenth century just as they are in the twentieth.

Probably the fogs of December were the most formidable because of their liability to be associated with severe frost during the darkest weeks of the year; but November, for reasons not far to seek, has always been the traditionally foggy month. It is the month when the general dampness of the autumn season resulting from falling temperature comes to a climax so that, when conditions favour radiation during the long nights, the mists form with special readiness in the hollows and low-lying places. In the country, warm sunshine may be lighting up the last tints of the forest foliage, while wreaths of mist are creeping along the woodland floor. In London, a couple of brilliant November days, with the wind falling light, are often the forerunner of a bad fog and should always be regarded with suspicion. Incidentally, I have not heard that the worst November fog ever frustrated the Lord Mayor's Show, but it would require more than metropolitan weather to do that. Did not a witty American once observe that if the Day of Judgment were to coincide with 9 November, Londoners would insist on seeing the Show first?

A change for the better

During the decade of the nineteen-hundreds, which practically coincided with the reign of King Edward VII, there was no noticeable change in the character of the London fog but during the nineteen-tens, the decade of the first world war, a change for the better came gradually to be suspected. Since then there has been a progressive improvement in each successive decade till now at the commencement of the nineteen-fifties we can definitely say that London fogs have lost their worst characteristics. Half a century ago a fog would vary its complexion between white, yellow, brown or black according to the amount of carbonaceous or sulphurous impurity in it. To-day such colour-grades have gone and most fogs in town would be described as yellowish white with little of the filth and choking pungency of former times. The overhead smoke hazes, again, are less black and more fleeting visitations than in the days of my boyhood and often merely mark a sudden shift of wind. All these facts prove that less crude smoke is being poured out of our chimneys partly because of more stringent factory regulations but much more because of the widespread substitution of gas and electricity for the open-grate fire.

Another change which has taken place of late years is this: that, except in the vicinity of the parks and near the river, fogs are notably less dense in the central built-up area than they are in the suburbs. This is no doubt due to better drainage and higher buildings which help to keep the air at ground level above its dew point. The horizontal structure of London ground fog to-day presents the interesting feature of very dense localized patches being embedded in much thinner drier stuff – fogs, as it were, within a fog. In the sharply defined thick patches the fog swirls and visibility is less than ten yards, reducing street traffic to a crawl, whereas, in the thinner areas, there is no visible swirling and, visibility being more than fifty yards, traffic can proceed with only a caution.

I do not know whether similar trends for the better have been taking place in other fog-stricken cities like Manchester and Glasgow; but I recently read that in Lyons, which a French meteorologist compares with London, a similar relation is found between the peripheral and central districts of the city for analogous reasons. It is just because London fogs, properly so-called, have been getting not only cleaner but also thinner that we so often nowadays hear of the city being “ringed round” with thick fog as in the prolonged occurrence at the end of November 1948.

In other words those great white water-fogs which sometimes stretch across England from end to end are as dense as they ever were. Perhaps my most interesting personal encounter with a fog of such a wide geographical range was upon boarding a London express at St. David's station, Exeter, one bitter December evening. On alighting at Paddington I saw the locomotive thickly encased in ice as a result of rushing through 170 miles of freezing fog between the Devonshire city and the capital.