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SECTION XVII. 



Experiments towards investigating 

 what plants or trees infecl the 

 furrounding air the leajl by night, 



119. I PLACED in four dif- 

 ferent gallon jars an equal quantity, 

 as near as I could, of leaves upon 

 their ftaiks of the following trees, 

 lime-tree) oak, laurocerafus^ walnut, 

 I placed all thofe jars over-night 

 in a room, each inverted upon a 

 dim ; in each jar was as much wa- 

 ter as would preferve the leaves 

 alive by keeping the ftalks wet. 

 Next morning I found the air of 

 all the jars contaminated : that of 

 the walnut-leaves was become unfit 

 for breathing, and extinguifhed 



flame ; 



