yet the difference is not so vei'v jxi'eat. For, just thinlc of how water 

 travels. It can run through a ]ii|ie that conducts it. Similarly heat 

 can run through many tilings that conduct it and are called con- 

 ductors. When heat travels in this way it is said to travel Ijy con- 

 duction. For instance, when an end of a poker is kept a good while 

 in the fire the heat travels the whole way to the handle and it may be- 

 come too hot to he held. Hence, iron is a conductor of heat. So, too, 

 are all other metals, but some conduct better than others. For in- 

 stance, put an iron or tin spoon and a solid silver spoon into a cup o£ 

 hot water and notice which liecomes hot at the upper end sooner. 

 You will then readily see that silver is a much better conductor than 

 iron or tin. (How can you test whether a silver spoon is solid or 

 merely plated with silver?) 



Suppose we next compare silver with copper. If you can find a 

 Canadian copper cent you will see that it is almost exactly the size of 

 a silver quarter. Put both of them at the same time on a hot stove 

 lid and quickly hold two matches on them and see which match burns 

 first, and so you will discover which is the better conductor, silver or 

 copper. If you can't easily find a Canadian cent, try a dime and a cop- 

 per cent. They will tell you the same tiling, but for a reason that you 

 should try to think out, you can't trust this form of the experiment 

 so much. To see how paper conducts, as compared with copper, use 

 two copper cents in one heap and a cent with a piece of pasteboard 

 about as thick as a cent on top of it as the other heap, and see which 

 will light a match first. Try also jjicces of glass, then flat stones and 

 china and other things, and you can easily make up a hst of poor con- 

 ductors and good conductors in this way. Compare also slate pencils 

 with nails of the same length, holding them upright on the stove 

 and trying on which you can hold your finger longer. Having these 

 wavs suggested to you, you will easily go on and discover many other 

 ways for yourself. 



But so far we have been talking of the conducting power of solids 

 only. Can we find out anything as to the conducting power of liquids 

 and gases? This is more difficult. Perhaps the best Avay is to get a 

 kind of very thin tu1je called a test-tube at a druggist's. Fill it with 

 cold water and hold it by the lower end at a slant so that the upper 

 end may be over a gas or damp flame. You will find that the water 

 may be boiling for some time at the top before it begins to feel hot 

 below. This shows that water is a very poor conductor. You may ask 

 why we don't hold it by the top and heat it below. It would heat 

 up much more quickly in that \y:\\, hut we would not be really testing 

 the conducting power of the liquid in that way. Perhaps you can 



