146 SCIENCE OF COMMON THINGS. 



Conducting power of water. Stoves and furnaces. 



the kettle does not readily pass through them to the 

 hand. 



37 Does the heat of the boiling kettle never get through the woollen or 

 paper kettle-liolder f 



Yes ; but though the kettle-holder became as hot as 

 the kettle itself, it would never feel so hot. 



038 Why would not the kettle-holder feel so hot as the kettle, when loth 

 are of the same temperature. 



Because it is a very lad conductor, and disposes of 

 its heat too slowly to be perceptible ; but metal (being 

 an excellent conductor) disposes of its heat so quickly, 

 that the sudden influx is painful. 



039 When we plunge our hands into a basin of water, why does it pro- 

 duce a sensation of cold f 



Because water is a better conductor than air ; and, as 

 it draws off the heat from our hands more rapidly, it 

 feels colder. 



040 Why does the conducting power of water make it feel colder than 

 air? 



Because it abstracts heat from our hands so rapidly 

 that we feel its loss ; but the air abstracts heat so very 

 slowly that its gradual loss is hardly perceptible. 



041 Is water a good conductor of heat ? 



No ; no liquid is a good conductor of heat ; but yet 

 water is a much better conductor than air. 



04S Why is water a bettei* conductor of heat than air 1 



Because it is more dense / and the conducting power 

 of any substance depends upon its solidity, or the close- 

 ness of its particles. 



043 How do you know that water is not a good conductor of heat ? 



Because it may be made to boil at its surface, without 

 imparting sufficient heat to melt ice a short distance 

 below the surface. 



044 Why are not liquors good conductors of heat f 



Because the heat (which should be transmitted) pro- 

 duces evaporation, and flies off in the vapor. 



045 // air is not a good conductor, how can we make use of it in 

 warming our houses by means of stoves and furnaces? 



