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are correct, there should be 1·2 milligrammes of soot at any moment in 100 cubic feet of Leeds air, on a working day. I made this calculation before I began my experiments, in order to ascertain approximately the quantity of soot I must prepare myself to deal with. The following is a diagram of the apparatus employed for estimating the solid matter in Leeds air.
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A is a leaden tube fixed through one of the windows of the Philosophical Hall, about 18 feet above the ground, and overlooking a side street where there was practically no traffic. Through a cork diaphragm within this, is fixed an open glass tube, B, consisting of a wide portion in front, and a narrow tail piece. The wide portion contains a carefully weighed plug of cotton wool, which filters the air and collects the solid matter. This plug was always dried and weighed against a similar plug. The glass tube, B, is connected with an empty bottle, C, and a Desaga water-jet aspirator, D, which is fixed into a large wash tower, E, so that air can be aspirated through B and C, and delivered to the experimental gas meter F for measurement. |
The apparatus was in work daily, except Sundays, from the middle of April to the middle of June, 1894, i.e., 50 days, 20 cubic feet of air being aspirated daily. The average of two sets of experiments gave 1·2 and 1·16 milligrammes respectively in 100 cubic feet, which comes very close to the estimated quantity. It is needless to state, that at the end of one day, the exposed end of the plug was perfectly black, from the accumulation of particles of soot. I think, then, that we shall not be far from the mark in accepting the figure I have given, viz.: 20 tons a day, or 6,000 tons, value £300, a year, as the minimum loss of fuel in the form of soot.
