8 GRAVITATION. 



which we have to deal at present, generally or 

 particularly, as I may require to illustrate my 

 subject. Here is the sort of matter which we 

 call water it is there ice [pointing to a block 

 of ice upon the table], there water [pointing 

 to the water boiling in a flask] here vapour 

 you see it issuing out from the top [of the 

 flask]. Do not suppose that that ice and that 

 water are two entirely different things, or that 

 the steam rising in bubbles and ascending in 

 vapour there is absolutely different from the 

 fluid water it may be different in some par- 

 ticulars, having reference to the amounts of 

 power which it contains ; but it is the same, 

 nevertheless, as the great ocean of water around 

 our globe, and I employ it here for the sake of 

 illustration, because if we look into it we shall 

 find that it supplies us with examples of all the 

 powers to which I shall have to refer. For in- 

 stance, here is water it is heavy; but let us 

 examine it with regard to the amount of its 

 heaviness, or its gravity. I have before me a 

 little glass vessel and scales [nearly equipoised 

 scales, one of which contained a half-pint glass 

 vessel], and the glass vessel is at present the 

 lighter of the two; but if I now take some 



