View report page

62
Soot.—The Coal Smoke Abatement Society published in the Lancet for
January 6th, 1912, a report of their records of the soot which fell during
twelve months in London. Two of the observation stations were in Westminster,
one in Buckingham Gate, the other in Horseferry Road. The total
deposit on an area of 4 square feet at the former was 71.9 grammes, at the
latter 60.3 grammes, compared with 27'8 grammes at a station at Sutton.
If the fall of soot were at the same rate over all London as at the Westminster
stations, it would equal 53,820 tons in the year. This would
contain 4,000 tons of ammonia, 5,000 tons of sulphur, reckoned as
sulphates, and 4.000 tons of chlorine in chlorides. These are due chiefly
to the faulty combustion of coal in domestic fires. The presence of so
much ammonia renders the rain neutral, or even slightly alkaline, which
probably encourages rather than discourages the disintegration of
building fabrics, since insoluble lime compounds—e.g., calcium carbonate
— readily yield ammonium carbonate and soluble calcium sulphate, and
ammonium carbonate attacks silica. Free sulphuric acid would also
attack lime compounds, but would not affect the silica appreciably.
The amount of insoluble deposit (soot, &c.), varies from 1/3 to ½ of
the total deposit in London
Fogs.—There has been a steady decrease in the number and density
of fogs in London in the last 25 years. In a series of years before
1884, fog was recorded on an average of 30 days in each year; in the
last ten years the average has fallen to 10 days, due to the efforts made
to abate the 6moke nuisance, and to the increasing use of gas and
electricity for heating.