120 FARADAY 



it changes in weight, in condition, in form, and in many 

 other qualities, it still is water; and whether we alter it into 

 ice by cooling, or whether we change it into steam by heat, 

 it increases in volume in the one case very strangely and 

 powerfully, and in the other case very largely and wonder- 

 fully. For instance, I will now take this thin cylinder, and 

 pour a little water into it, and, seeing how much water I 

 pour in, you may easily estimate for yourselves how high it 

 will rise in the vessel: it will cover the bottom about two 

 inches. I am now about to convert the water into steam 

 for the purpose of showing to you the different volumes 

 which water occupies in its different states of water and 

 steam. 



Let us now take the case of water changing into ice : we 

 can effect that by cooling it in a mixture of salt and 

 pounded ice( u ) and I shall do so to show you the expan- 

 sion of water into a thing of larger bulk when it is so 

 changed. These bottles [holding one] are made of strong 

 cast iron, very strong and very thick I suppose they are 

 the third of an inch in thickness; they are very carefully 

 filled with water, so as to exclude all air, and then they are 

 screwed down tight. We shall see that when we freeze the 

 water in these iron vessels, they will not be able to hold the 

 ice, and the expansion within them will break them in pieces 

 as these [pointing to some fragments] are broken, which 

 have been bottles of exactly the same kind. I am about to 

 put these two bottles into that mixture of ice and salt for 

 the purpose of showing that when water becomes ice it 

 changes in volume in this extraordinary way. 



In the mean time, look at the change which has taken 

 place in the water to which we have applied heat ; it is losing 

 its fluid state. You may tell this by two or three circum- 

 stances. I have covered the mouth of this glass flask, in 

 which water is boiling, with a watch-glass. Do you see 

 what happens ? It rattles away like a valve chattering, be- 

 cause the steam rising from the boiling water sends the 

 valve up and down, and forces itself out, and so makes it 

 clatter. You can very easily perceive that the flask is quite 



u A mixture of salt and pounded ice reduces the temperature from 33 F. 

 to zero, the ice at the same time becoming fluid. 



