lxViii CONTENTS. 



Se&« XVII. Experiments towards invejiigating 

 what plants or trees infect the fur rounding 

 the air lea ft by night} p. zyo 



JLVIII. Experiments /hewing that toe purefl 

 .dephlogijlicated air, and the greatefl quantity, 

 is yielded by full-grown leaves, 272 



XIX. Experiments fjewing that the fan by 

 iifelf without the ajfif lance of plants, does 

 not improve air, but renders it rather worfe 9 



274 



XX. Experiments tending to invefiigaie the mojl 

 accurate and expeditious way of putting corn- 

 men air to the tefl, o?i purpjfe to judge of the 

 (cilubrity of any country. 216 



Fo/ljcript, 288 



ON 



