BY LEAVES. IQT 



Dr. Priestley was the first who suggested this last- 

 mentioned quality in vegetables. He ascertained their 

 r)ower of absorbing carbonic acid gas, denominated by 

 him fixed air, and giving out oxygen gas, or pure re- 

 spirable air. It was also his opinion that leaves imbib- 

 ed the former by their upper, and gave out the latter 

 by their under surface. He found some aquatic or 

 marsh plants extremely powerful in this respect, es- 

 pecially the Willow-herb or Epilobium, and the Confer- 

 va, a minute branching cotton-like vegetable which 

 grows in putrid water, and the production of which, in 

 water become foul from long keeping on ship- board, 

 Dr. Priestley judged to operate principally in restoring 

 that fluid to a state fit for use. 



Dr. Ingenhousz, pursuing Dr. Priestley's inquiries, 

 found light to be necessary to these functions, and that, 

 in the dark, leaves gave out a bad air. He observed 

 moreover that fruits and flowers almost invariably gave 

 out a bad, or carbonic, air, but more especially in the 

 dark. He probably carries his ideas of the deleterious 

 eflfects of this air on animal life, too far ; for no mischief 

 has ever happened, as far as common experience goes, 

 to persons sleeping in apple or olive chambers, neither do 

 the inhabitants of the confined huts inCovent-garden mar- 

 ket apparently suffer, from living day and night among 

 heaps of drying herbs. Mischiefs have unquestionably 

 arisen from flowers in a bed-room, or any other confined 

 apartment, but that is to be attributed to their perfumed 

 effluvia. So the bad effects, observed by Jacqnin, of Lobe- 

 lia longijiora on the air of a hot-house, the danger incur- 

 red by those who sleep under the Manchineel-tree, Hip- 



