Chap. 2.] Purt Air by Means of Vegetatim. 375 

 quantities from water, efpecially from pump water, 

 which, when cxpofed to the fun, emits air flowly ; 

 but after it has remained fb for a considerable time, a 

 green matter adheres to the bottom and fides of the 

 glafs veffel in which it remained - y afterwards it emits 

 pure air in great quantities, and continues to do fo for 

 a long time after the green matter has exhibited fymp- 

 toms of decay by turning yellow. 



Dr. Ingenhoufz rightly fuppofed this green matter 

 to belong to the vegetable- kingdom, and procured 

 pure air by putting the leaves of plants into water, and 

 expofing them to the fun. He obferves, that of land 

 vegetables the fitteft for this pnrpofe are the poifonous 

 plants, fuch as hyofcyamus, laurocerafus, night-fhade, 

 &c. But he extracted the pureft air from fome aqua^- 

 tic vegetables, and from turpentine trees, but efpecially 

 from the green matter he collected from a ftone 

 trough, which had been kept filled with water from 4 

 fpring near the high road. 



While Dr. PrieflLey was engaged in a feries of ex- 

 periments to enable him to purify contaminated air, 

 he difcovered that vegetables anfwered this purpofe 

 moft effectually. The experiment by which he illuf- 

 trates his afTertion was this - } having rendered a quantity 

 of air very noxious, by mice breathing and dying in it, 

 he divided it into two receivers inverted in water, intro 

 ducing a fprig of mint into one of them, and keeping 

 the other receiver with the contaminated air in it alone. 

 He found, in about eight or nine days after, that the air 

 of the receiver, info which he had introduced the fprig 

 of mint, had become refpirable ; for a moufe lived 

 very well in this, but died immediately upon being 

 introduced into the other receiver, containing the con-, 

 taminated air alone. 



B b 4 It 



