If air pollution perturbed natural cycles in the city, at the same time the 'smoke nuisance' imposed its own sustained rhythms on urban life that fluctuated daily, weekly and seasonally. Changing climatic conditions meant that day to day concentrations of smoke pollution varied widely in urban-industrial areas. However, levels of smoke pollution also ebbed and flowed in line with relatively settled patterns of coal consumption in factories and private houses. On a weekday the smoke cloud rapidly expanded between the hours of 6 and 7 a.m. in Manchester, as domestic fires were rekindled and the chimneys of manufacturing industry -largely dormant at night - belched back into life. The smoke was at its thickest around 11 a.m., with a subordinate peak at 5 p.m.; periods which coincided with the preparation of midday and evening meals. 189 Pollution gradually waned after this point, as mills and factories wound down and domestic fires were allowed to burn low at the end of the day. The smoke cloud contracted to its lowest ebb between the hours of 1 0 p.m. and 4 a.m., although it rarely happened that there was no smoke at all during the 24 hours. 19o On Sundays the peaks of the smoke cycle occurred one or two hours later than on a weekday, as the workers liked to sleep late on their day off. Generally speaking, Sunday was the day on which Manchester's air was least polluted as the city's factories were closed. However, this rule of thumb did not hold true for many non-industrial towns and cities, nor for the crowded suburbs of industrial towns, where smoke pollution on Sundays was thought to exceed that of the average weekday.191 The quantity of extra fuel required for cooking the main meal of the week, Sunday dinner, was held to be the major culprit. A prodigious amount of roasting, grilling, baking, frying and boiling produced a surfeit of
smoke from many thousands of domestic chimney pots. The PubLic HeaLth Engineer, for example, reported that the urban smoke haze was at its worst on Sundays 'when extra cooking took place over the widest area'. 192
ILLustration 3. Domestic Chimneys at Manchester.