92 



NATURE TEACHING 



Pour a little lime-water into a tumbler or small 

 glass, and by means of a tube (of glass, bamboo or 

 a straw) pass the breath from the lungs through the 

 lime-water, which will soon become cloudy from the 

 formation of carbonate of lime as in the last experiment 

 (see Fig. n). If the breathing is continued for a long 

 time the lime-water will become clear again, owing to 

 the chalk being dissolved in the excess of carbon dioxide. 



FlG. ii. Breathing into 

 lime-water to show that 

 the breath contains car- 

 bon dioxide. 



FlG. 12. Experiment to 

 show that plants breathe 

 out carbon dioxide. 



Into a similar bottle, corked or covered with a piece 

 of glass, place about a handful of the young tips of 

 leafy shoots, or opening flower-buds for instance, man- 

 golds (see Fig. 12). Add a very little water to keep 

 them moist, and put away in the dark for about six hours. 

 Test as before with lime-water, when it should be found 

 that once again we have had carbon dioxide produced 

 in considerable amount. Repeat the experiment with 

 similar leafy shoots, but, instead of placing them in the 



