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The influence of plants on the 

 air of a room in which they are 

 kept is different in the night from 

 what it is in the day. In the day 

 plants are apt to contribute fome- 

 what to purify the air of the room, 

 if they are placed fo as to receive 

 all the light of the fun poflible : 

 if they are placed fo as not to re- 

 ceive the direct influence of the 

 fun, but to be free from any fhade, 

 they feein to have no influence at 

 all, either in improving the air of 

 the room or in fouling it. But 

 when they are placed in a part of 

 the room the moft remote from the 

 windows, fo as to be much ihaded, 

 they are apt to render the air of 

 the room more or lefs impure, in 

 proportion to their lize, and to the 

 more or lefs degree of light of the 

 place where they Hand. At night 



they 



