﻿THE AIR OF TOWNS. 15 



teet, wbicb we took as tlie smoke-iufected area, tlie amount of carbonic 

 acid would be about 1 per cent higber in twenty-four bours, or Avould 

 bave to be renewed fifty times in twelve bours to keep down tbe aver- 

 age amount of carbonic acid to 0.04 per cent. 



Let us attack tbe problem in anotber way. In Professor Eoberts- 

 Austen's report on tbe London smoke- abatement exbibition a large 

 number of analyses are given, from wbicb it is easy to calculate tbe 

 weigbt of smoke from coal burnt in bouse fires. Tbese analyses refer 

 to diiferent kinds of smoke-preventing domestic fire grates burning 

 different kinds of coal. According to tbese results about 5 -per cent of 

 tbe coal burnt gets into tbe air. Mr. Kussell, of tbe Yorksbire Col- 

 lege, and myself experimented in tbe same direction and arrived inde- 

 pendently at tbe same conclusion, witbout bavin g referred to tbe 

 results of Eoberts- Austen's analyses. 



If we take 100,000 tons as tbe bouse consumption of coal in tbe year 

 for Leeds, tbis is equivalent to about 11 tons in twenty-four bours 

 tbrougbout tbe year. If we allow aa equal amount for factory cbimneys, 

 tbis brings it to 22 tons in twenty-four bours. Or if we follow Scbeurer- 

 Kestner and take one-balf to tbree-fourtbs per cent as tbe amount of 

 coal given oft' as smoke from boiler furnaces, tben if Leeds consumes 

 1,500,000 tons of coal a year, or 4,000 tons a day, one-balf per cent ui^on 

 tbis is equivalent to 20 tons a day. So you see tbat wbicbever way 

 we work our calculation we can not get below 20 tons of smoke a day, 

 and I consider tbat tbis figure represents a minimum quantity ratber 

 tban tbe true average. 



And now as to tbe amount tbat falls. Tbe winter before last snow 

 fell on January 7. A sample covering 1 square yard was carefully 

 removed from a gravestone in tbe parisb cburcbyard a sbort time after 

 tbe fall ceased. Tbe snow was melted and analyzed. Fresb samples 

 were taken and analyzed on tbe following tbree days. Tbey contained 

 a variety of tilings in solution — ammonium sulpbate, sulpbate of lime, 

 and free sulpburic acid, all mainly derived from coal. We need not 

 trouble ourselves about tbese at i^resent, altliougb we can not mask tbe 

 injury wbicb tbis corrosive acid produces upon vegetation and tbe stone 

 and brick work of our buildings. 



It is tbe solid matter wbicb now concerns us. 



Here are some of tbe samples (fig. 16) : A was collected on tbe first 

 day, B on tbe second, C on tbe tbird, and I) on tbe fourtb. Tbe accu- 

 mulation of soot is evident from tbe deptb of color. 



Tlie weigbt of solid matter carried down, as determined from tbe first 

 sample, was equivalent to 16 bundredweigbt on tbe square mile. Tbe 

 additional weigbt of soot wbicb accumulated eacb day was equivalent 

 to 4 bundredweigbt on tbe square mile; or, if we take a smaller quantity 

 as an average over tbe 4 square miles of tbe city, we arrive at tbe daily 

 smoke fall of about one-balf ton. 



It is impossible to say wbat proportion of tbe soot in tbe air, during 

 tbe snowfall, tbe 16 bundredweigbt represents, but it all points in one 



