74 SCIENCE PRIMERS. [MATERIAL 



the molecules of the other until there is the same 

 proportion of each everywhere. In like manner, 

 sand and sugar may be (and unfortunately often are) 

 mixed, without any change in the properties of either, 

 or in the space which they primitively occupied. 



On the other hand, oil and water will not mix, how- 

 ever much you may stir the two together ; and the oil, 

 being the lighter, rises to the top as soon as the fluid 

 is quiet. Nor will quicksilver and water mix, but the 

 quicksilver, being very much heavier than the water, 

 rushes to the bottom of the vessel into which the two 

 are put. Neither will sand nor iron filings mix with 

 water ; as heavier bodies, they also sink to the bottom. 

 Nor does powdered ice, though it is water in another 

 shape, mix with ice cold water; as a lighter body, it 

 floats at the top. 



52. Mixture followed by Increase of Den- 

 sity ; Alcohol and Water. 



Strong spirit, or alcohol, is a clear transparent fluid 

 which looks like water, but is a very different substance. 

 For example, it boils at a much lower temperature, it 

 burns with a; blue flame, it has intoxicating properties, 

 and, like oil, it is very much lighter than water. Hence 

 if coloured spirit is poured gently upon the surface of 

 water the spirit rests upon the water. Suppose, now, 

 that we take a tall measure graduated into ten equal 

 parts. Fill the lower five with water, and then, very 

 gently, pour in the strongest alcohol, coloured in 

 some way, until the tenth mark is reached. We shall 

 have five volumes of water below, and an equal quan- 

 tity, or five volumes, of coloured alcohol above. 

 Where the two are in contact, the colour will be 



