236 M. Marcet on the Changes which tlie Atmosphere 



exposed to the light, but not in the direct rays of the sun, for 

 nine hours. At the expiration of this time, the volume of the 

 air in the receiver was 32.95 cubic feet. The analysis furnished 

 the following result : — The receiver contained, before the ex- 

 periment, of nitrogen 25.58 cubic feet, of oxygen 6.79, = 32.37 ; 

 after the experiment, nitrogen 25.37 cubic feet, oxygen .67, car- 

 bonic acid 6.91, = 32.95. 



It will be observed that, whilst the mushrooms remained un- 

 der the receiver, nearly the whole of the oxygen of the air, viz. 

 6.12, combined with the carbon of the vegetable, to form an 

 equal volume of carbonic acid gas. The mushrooms also evolved 

 an additional .79. Of nitrogen .21 disappeared, a very minute 

 quantity, which may be owing partly to an absorption arising 

 from the porosity of the mushrooms, and partly, perhaps, to an 

 error in the experiment. 



The preceding experiment was repeated by placing mush- 

 rooms, of the same kind and weight, under a receiver contain- 

 ing 32.37 cubic feet of air, and allowing it to remain for ten 

 hours in complete darkness, the thermometer being at 61° Fahr. 

 At the expiration of this time the volume of air was 32.66. 

 The following is the result of the analysis : — The receiver con- 

 tained, before the experiment, of nitrogen 25.58, of oxygen 

 6-79, = 32.37 ; after the experiment, of nitrogen 25.49, of oxy- 

 gen .73, of carbonic acid 6.44, = 32.66. 



From this it appears that the action of the mushrooms upon 

 the atmosphere during the night differs little from that which 

 goes on during the day; perhaps it appears somewhat less ener- 

 getic, since it required twelve hours during the night to produce 

 a quantity of carbonic acid somewhat smaller than that whicli 

 had been produced in nine hours during the day. 



The preceding experiment was repeated a third time with 

 the species Lycoperdon bovista, upon three plants taken at a 

 more advanced age, when the vegetation almost appeared to 

 have ceased, and when this mushroom, instead of being of a 

 fleshy consistence, appears to be only a bag full of fine powder. 

 They, together, weighed 72 grains ; the thermometer stood at 

 72° Fahr. Having been left for twelve hours, six during the 

 day, and six at night, under a receiver containing 29.17 cubic 

 feet of air, it was found, at the conclusion of this time, that the 



