As fog has now been abolished both on sea and land, and as few of the present generation have even seen one, it may not be out of place to give a few lines on the subject of fogs in general, and the London fogs in particular, which through local peculiarities differed from all others. A fog was simply watery vapor rising from the marshy surface of the land or from the sea, or condensed into a cloud from the saturated atmosphere. In my day, fogs were a great danger at sea, for people then travelled by means of steamships that sailed upon the surface of the ocean.

London at the end of the 19th century consumed vast quantities of a soft bituminous coal for the purpose of heating rooms and of preparing food. In the morning and during the day, clouds of black smoke were poured forth from thousands of chimneys. When a mass of white vapor arose in the night these clouds of smoke fell upon the fog, pressing it down, filtering slowly through it, and adding to its density. The sun would have absorbed the fog but for the layer of smoke that lay thick above the vapor and prevented the rays reaching it. Once this condition of things prevailed, nothing could clear London but a breeze of wind from any direction. London frequently had a seven days’ fog, and sometimes a seven days’ calm, but these two conditions never coincided until the last year of the last century. The coincidence, as everyone knows, meant death—death so wholesale that no war the earth has ever seen left such slaughter behind it. To understand the situation, one has only to imagine the fog as taking the place of the ashes at Pompeii, and the coal-smoke as being the lava that covered it. The result to the inhabitants in both cases was exactly the same.