Pioneer Laborers 15 



can be dissolved, while the sun draws up from it almost 

 pure water, leaving the salts behind to accumulate and 

 help to feed the crops of seaweed, besides providing 

 material for the skeletons of corals and sponges and the 

 shells and bones of other sea-creatures. All plants, then, 

 are alike in this, that they live upon other food besides 

 mere air and water. 



We may easily satisfy ourselves of this by burning a 

 bit of wood, a few grains of corn, or any other vegetable 

 matter. When it has burned as long as there is anything 

 to burn, and all gases and water it contained are driven 

 away, a small quantity of ash will remain, consisting of 

 salts, or compounds of various metals. The whole 

 amount is usually very small — so small that we might per- 

 haps be disposed to think it could not be of any very great 

 consequence. 



If, for instance, we were to burn a hundred grains of 

 wheat so thoroughly that nothing but ash remained, we 

 should find the whole amount of this to be equal to about 

 two of the grains, or less. 



However, **many a mickle makes a muckle, " and 

 when we consider, not single plants or a handful of grain, 

 but a whole crop, the amount of mineral matter becomes 

 large enough to look important. Thus, while a pinch or 

 two of dust might represent the entire amount of ash of 

 all sorts in a single turnip or carrot, there are, on an 

 average, about forty pounds of lime alone in twenty-two 

 tons of turnips, more in proportion in the carrots, and 

 very much more in an equal weight of clover. 



The mineral substances chiefly taken up by plants are 

 sulphur, phosphorus, silica, potash, soda, lime, iron, 

 magnesia, manganese, together with mineral compounds 



