Fixed Ailr on Vegetation. 365 



feveral of your experiments, that during feven 

 hours of the day, viz. fronn 10, A. M. to 5, P. M. 

 the plants, you employed, were expofed to varying 

 proportions of fixed air, fel^om exceeding ». the 

 proportion of air, contained in the vefTel, and 

 never lefs than ^, But, from 5 o'clock in the 

 evening till 10, the fucceeding day, the quan- 

 tity of fixed air feems to have varied, from | to -rV 

 of the whole air. Now a plant expofed to fuch 

 diverfified proportions of air, paffing too in a 

 ilream through the veflel, mufl: be in a favour- 

 able ftate, both for exhalation, and confequently 

 for the procefs of inhalation alfo. 



I am, dear Sir, 



With the mofl perfefl regard. 



Your faithful, afTeftionate Friend, 



THOMAS HENRY. 



Manchester, May 12, iji^-. 



Observations 



