IN PHYSICS. 225 



of safe> pipes of water are used, which absorb the heat 

 and render it latent. 



57. Why can you heat water quicker in a tin than a 

 china cup ? 



Because the metal is a better conductor of heat than 

 the china. 



58. Why will" a woollen blanket keep ice from melting? 

 The woollen is a non-conductor of heat. 



59. Does dew form under trees ? 



The trees reflect back the heat radiated by the earth, 

 grass, etc., and so prevent the temperature, in general, 

 from sinking to the dew-point. 



60. What is the principle of heating by steam ? 



(See P&yszcs, p. 206.) 



6 1. Why is a gun firing blank cartridges more heated 

 than one firing balls ? 



(See Key, p. 207, Question 53.) 



62. What is the cause of " cloud-capped" mountains ? 



(See Physics, p. 197.) 



63. Show how the glass in a hot-house acts as a trap to 

 catch the sunbeam. 



(See Physics, p. 194.) 



64. Does the heat of the sun come in through our win- 

 dows ? 



(See Physics, p. 194.) 



65. Does the heat of our stoves pass out in the same 

 way? 



(See Pkysics, p. 194.) 



