SOILS AND THEIR COMPOSITION 159 



Pour off the brown liquid into another vessel. The sand 

 and small stones will be left at the bottom. Weigh them. 

 Then take your discoloured water and filter it. The 

 stuff on the filter paper wiU be clay alumina. So far so 

 good. But when we tabulate our results we shall prob- 

 ably find that we are short by a small amount of weight. 

 What about that odd half ounce ? It is a highly import- 

 ant half-ounce, for it contains the volatile gases, am- 

 monia, carbonic acid, nitrogen, etc., and also, as our 

 method is only a rough one, there wiU be small traces of 

 iron, sulphur, magnesia and other elements that we 

 have missed, whilst to complete the experiment we 

 should put our filtered water into a clean fireproof pan 

 and boil it off to get the soluble salts which will be found 

 as a small white residue at the bottom. 



Putting the results together we are able to judge 

 whether our soil is what it should be. Rough analyses 

 of the three principal soils are shown below : 



Sand. Loam. Clay 



Moisture . 2 oz. 3 oz. 4 oz. 



Organic substances . . . . 2J „ 5 „ 2J „ 



Grit 8 „ 3J „ IJ „ 



Clay Alumina 3 „ 4 „ 8 „ 



Volatile matter, soluble salts and 



loss I „ J „ J „ 



Totals 16 oz. 16 oz. 16 oz. 



Thus we can at once see to what extent to correct the 

 texture of our soil, always aiming at the composition of 

 loam. 



We now come to the question, how do plants assimi- 

 late nutriment ? To save needless description, I propose 

 to draw another little sketch or two, showing a plant, 

 root and all, in the soil. In fig. 1 we see a cauHflower 

 which is growing in good ground, well tended. The 

 latter point is highly important, as, whether the ground 

 be a rich nutritious loam, properly drained and dug, 



