22 
229. By the former experiment (227. ), it was 
proved that the oxygen gas of the air was in part 
consumed, and the same circumstance may be pre- 
sumed to have happened in this case, from the gra- 
dual decline and final cessation of growth which took 
place. The formation of carbonic acid may also be 
presumed, from the continued rise of the water into 
the jar ; but to prove this more clearly, we raised 
the jar, and passed the alkaline solution into a small 
jar filled with mercury, and inverted in a bason of 
that fluid. A small quantity of diluted sulphuric 
acid was then added to the solution, which caused 
an immediate effervescence, and the extrication of 
nearly two cubic inches of carbonic acid gas, which 
were afterwards entirely attracted, with the usual 
phenomena, by pure lime water. These experiments 
therefore prove, that by the growth of young beans, 
which contain no white parts, but, on the contrary, 
have both leaves and stems of a deep green colour, 
the oxygen gas of the air is changed into carbonic 
acid, in the same manner as by the mustard plants 
mentioned (32.) in the former part of our Inquiry. Si- 
milar results were obtained by placing radishes, a plant 
of hydrangia mutabilis, and some others, in like cir- 
cumstances. These experiments were likewise seen 
by Mr Murray, who considers them as obviating 
entirely the objection which he had previously sug- 
gested*. 
230. To remove any objection that may be made 
to the early age of these plants, or to their being en- 
* Syst. Chem. v, iv. p. 47. 2d edit. 
