ON THE AIE AND RAIN OP MANCHESTEB. 213 



of it at least is entirely so, but an exception must be made 

 of that which is alive. 



It becomes clear from the experiments, that rain water in 

 town districts, even a few miles distant from a town, is not a 

 pure water for drinking, and that if it could be got direct 

 from the clouds in large quantities, we must still resort to 

 collecting it on the ground in order to get it pure. The im- 

 purities of rain are completely removed by filtration through 

 the soil; when that is done there is no more nauseous taste 

 of oil or of soot, and it becomes perfectly transparent. 



The presence of free sulphuric acid in the air sufficiently 

 explains the fading of colours in prints and dyed goods, the 

 rusting of metals, and the rotting of blinds. 



It has been observed that the lower portions of projecting 

 stones in buildings were more apt to crumble away than the 

 upper ; as the rain falls down and lodges there and by degrees 

 evaporates, the acid will be left and the action on the stone 

 be much increased. 



I do not mean to say that all the rain is acid — it is often 

 found with so much ammonia in it as to overcome the acidity ; 

 but in general, I think, the acid prevails in the town. But 

 even if alkaline when it falls, it becomes acid on standing, 

 and especially on boiling down, as the ammonia in these 

 cases is separated from its acid. 



A specimen taken in Greenheys fields, half a mile from the 

 extreme south-west of Manchester, wind blowing west, had a 

 peculiarly oily and bitter taste when freshly caught. A per- 

 son to whom I gave some of it to taste, supposed it had been 

 put into a glass in which castor oil had been put. I had col- 

 lected the water in a large meat dish, which had been very 

 carefully cleaned, and was then set on a stand about two feet 

 from the ground, during the rain. Thinking it possible that 

 some fatty matter might have been adhering to the vessel in 

 spite of all my care, and not being inclined to believe that 

 such an amount of impurity could be found in that place, I 



