25 



Tarnation. 1 By many its proportion has been rated 

 at ~ j but Berthollet considers this estimate as 

 much too high *, and Dal ton makes it amount only 

 to lo!^ a quantity much too inconsiderable to ex- 

 ert any sensible effect. When also M. de Saussure 

 abstracted the carbonic acid from the air, previous 

 to placing the seeds (7.) in it, germination went on 

 as well as where this had not been done ; and, on 

 the other hand, this process continued to proceed 

 when the acid was removed, as soon as formed (8.) 

 by an alkaline solution, as when it was suffered to 

 remain. It has been said, however, that when it is 

 abstracted, by means of lime, from the air in which 

 seeds are growing, the progress of their growth is 

 retarded. The lime, indeed, does abstract the car- 

 bonic acid in the same manner as we have seen the 

 alkaline solution to do : and, a firiori, there seems 

 no reason why its abstraction should in one case be 

 more prejudicial than in the other. But this ab- 

 straction of the acid by the lime is carried on only 

 after it has imbibed water; and we found, that when 

 a quantity of powdered lime was placed underneath 

 some peas growing in a jar inverted over mercury, 

 it presently began to swell, the jar continued quite 

 dry, and the peas germinated very imperfectly, be- 

 ing reduced nearly to half their bulk. Thus, they 

 \vere deprived too rapidly of their moisture to en- 

 able them to grow, in the same manner as when 

 they are too freely exposed (18.) to the air. . In 



* Chemical Statics, vol. i, p. 375. 



f Manchester Memoirs, vol. i. new series. 



