ON THE AIR AKD RAIN OF MANCHESTER. 



215 



It contains many of the green monads, singly and in groups. 

 These increased immensely, and were in numbers much greater 

 than in the field rain. There were also some lengthened bodies 

 somewhat resembling the gallionella, but I cannot speak with 

 certainty of the species. 



This water is acid, and on boiling becomes very acid, until 

 it may be readily tasted as sour. 



The residue when burnt gave off ammoniacal vapours, and 

 shewed also the presence of albuminous compounds. The 

 sides of the vessel were covered over with an oily or tarry 

 substance. 



The ashes were neutral, and consisted of sulphates; sul- 

 phate of lime and soda being amongst them. 



These two specimens are characteristic of the places ; they 

 are not extreme points by any means. One is not very far in 

 the town, and the other is not very far out of the town. I 

 am sorry I have not obtained extreme cases, but the difference 

 is sufficient as a point to start from. The one leaves alkaline 

 ash, the other neutral ash. In the fields the amount of acid 

 is not sufficient to neutralize the bases which are in union 

 with the organic matter, and the residue is therefore alkaline ; 

 but in the town the amount of acid is equal, or in excess; 

 what is in excess is driven off, and enough remains to saturate 

 the bases, which become then neutral salts. 



The increase of amount of organic matter is not so apparent 

 from the table of quantities which I have drawn up ; but I 

 rely more on observing these living creatures, which are the 

 sure indications of its presence. And they shew also that if 

 there was not a great increase of it in the town, it was at least 

 in a state peculiarly organizable. 



Again, Greenheys fields, on the same day. — This water has 

 a blackish deposit ; a few monads may be seen at once ; taste 

 when first got very greasy ; after standing a while this taste 

 becomes bitter, like rotten leaves; flat, like all the speci> 



