6 What is the soil made of? 



with grit, some of which was moving slowly down and 

 some not at all Grit can therefore be separated from 

 the rest of the soil by water. 



This separation can be shown very well by the 

 following experiment. Rub ten grams of finely powdered 

 soil with a little water (rain water is better than tap 

 water), and carefully pour the muddy liquid into a 

 large glass jar. Add more water to the rest of the 

 soil, shake, and again pour the liquid into the jar ; go 

 on doing this till the jar is full. Then get some more 

 jars and still keep on till the liquid is no longer muddy 

 but nearly clear. The part of the soil that remains 

 behind and will not float over into the jars is at once 

 seen to be made up of small stones, grit, and sand. 

 Set the jars aside and look at them after a day or so. 

 The liquid remains muddy for some time, but then it 

 clears and a thick black sediment gathers at the bottom. 

 If now you very carefully pour the liquid off you can 

 collect the sediments : they are soft and sticky, and 

 can be moulded into patterns like clay. In order to 

 see if they really contain clay we must do the experi- 

 ment again, but use pure clay from a brick yard, or 

 modelling clay, instead of soil. The muddy liquid is 

 obtained as before, it takes a long time to settle, but 

 in the end it gives a sediment so much like that from 

 the soil, except in colour, that we shall be safe in saying 

 that the sediments in the jars contain the clay from the 

 soil. And thus we have been able to separate the sticky 

 part of the soil — the clay — from the gritty or sandy 

 part which is not at all sticky. We may even be able 

 to find out something more. If we leave the soil sedi- 

 ment and the clay sediment on separate tin lids to dry, 

 and then examine them carefully we may find that the 



