JtODEBN IDEAS OF 8AKITARY ECONOMY. 



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continually rising up into the atmosphere. If the air were 

 constantly clear, we should then have very diminished evils of 

 the kind, as this constant ventilation of the town would take 

 place ; but when it is clouded and moist, an entirely different 

 state of things occurs. The acid and other impurities become 

 dissolved in the moisture, and the black parts of the smoke 

 become wet and heavy. At this time the air becomes very 

 acid, and the atmosphere, as we approach the more crowded 

 parts of the town, becomes sensibly deteriorated. This must 

 have been observed by many. If the day be foggy, this 

 takes place in still greater force, and these floating particles 

 of liquid must have a strong influence on those who are 

 subject to coughs, or are otherwise delicate, being, as they 

 are, solutions of acid and acid salts. This is one of the ways 

 in which we suffer from a moist climate, and it is another 

 reason why we should do all we can to dry it, by removing 

 the water when it does fall, and allowing only that which is 

 pure to be exposed to evaporation. 



According to one analysis of a coal used in Derbyshire, 

 which is rather below what is a good deal used here, I believe, 

 there is one quarter of a ton of sulphur obtained from 100 tons 

 of coal burnt. This would give 15 cwt. of strong sulpliuric 

 acid, which itself would be a great deal to exist in the atmo- 

 sphere at a time, if we take Manchester as four miles square, 

 and suppose a space 300 feet high; but the calculation 

 is of little value unless we know the amount of coal con- 

 sumed. I do not know how much is burnt in one day, 

 but it will be seen from this to how great an accumula- 

 tion of bad air we are exposed, whenever an interruption 

 occurs to the natural ventilation of the town. This interrup- 

 tion occurs not from entire calmness of the atmosphere, such 

 a thing is rare with us, and if it did occur in clear weather, 

 would not be a great inconvenience, unless it lasted long ; on 

 such occasions the gases escape readily, especially when with 

 clearness there is warmth. But the interruption to ventilation 



