82 COMPANION TO TROPICAL READERS 



diameter by pasting paper over a very light framework; 

 put two fine wires crossing one another at the opening 

 at the bottom; tie a sponge where the wires meet, and 

 saturate it with alcohol; set fire to the sponge and the 

 balloon will rise. This experiment should only be done 

 by the teacher. 



Expt. 198. Soil both absorbs and gives out Heat 

 more quickly than Water. Heat at the same time 

 over the same fire a tin filled with soil and another 

 of equal size filled with water, for five to ten minutes; 

 observe which gets hotter. Allow both to cool, and 

 observe which cools first, remembering that the soil was 

 the hotter. 



VENTILATION 



(See Tropical Readers, Book II, pp. 171-174.) 



Expt. 199. A well -ventilated Building. Write a 

 description of any building that you consider well ven- 

 tilated. 



Expt. 200. A badly-ventilated Building. Write a 

 description of any building that you consider to be 

 badly ventilated. 



Expt. 201. Small Quantity of Carbon Dioxide in Air 

 taken into Lungs. Leave a vessel of lime water ex- 

 posed to the air. Observe that it turns milky, but very 

 slowly, as there is only - 04 per cent of carbon dioxide 

 present in the air which is taken into the lungs. 



Expt. 202. Larger Quantity of Carbon Dioxide (about 

 4 7 per cent) found in Air breathed out. Breathe 

 through a glass tube or small bamboo into a vessel of 

 lime water. A heavy milky precipitate will be formed. 



Expt. 203. Carbon Dioxide on Floor of Sleeping- 

 room. Put a saucer with lime-water on the floor of 



