THE NATURE OF THE SOIL 



We had best, therefore, heat it to exactly the 

 temperature at which water boils. We shall then 

 be sure that the water is driven off, and at the same 

 time not make it hotter than is necessary. We can 

 do this most easily by drying it in a water-lath. 



That is to say, you 

 place the mould in a 

 metal case surrounded by 

 water contained in an 

 outer case, and heat the 

 whole apparatus over a 

 flame. 



The water in the outer 

 case boils and heats the 

 soil to just the right 

 temperature. 



Weigh out about one ounce of the soil in a tin dish 

 (the round lid of a tobacco tin will do very well), 

 and place it in the inner case of the water-bath, and 

 heat it there for about an hour. 



Then take it out, let it cool, and weigh again. 

 It will now weigh much less than before. We 

 cannot, however, be sure that all the water is gone. 

 Put it back in the water-bath, heat for another half 

 hour, and again weigh. 



If the weight is the same as in the second 

 weighing, we may be sure that all the water is 

 gone. The soil will lose perhaps 15 or 20 per cent 

 of its weight, showing the amount of water it 

 contains. 



FIG. 



