CRGANIC MATTER OF THE SOIL CONTAINS NITROGEN. 409 



4°. Further, quick-lime is soluble in water, and hence every shower 

 that falls and sinks into the soil carries with it a portion of lime, so 

 long as any of it remains in the caustic state. It thus reaches acid 

 matters that lie beneath the surface, and alters and ameliorates even 

 tlie subsoil itself 



5°. It is not a small additional recommendation of quick-lime, that 

 by burning it loses about 44 per cent, of its weight, thus enabling 

 nearly twice the quantity to be conveyed from place to place at the 

 same cost of transport. This not only causes a direct saving of 

 money, — as when the burned chalk of Antrim is carried by sea to 

 the Ayrshire coasts — but an additional saving of labor also upon the 

 farm, — where the number of hands and horses is often barely suffici- 

 ent for the necessary work. 



§ 29. Action of lime on organic substances which contain nitrogen. 



I have hitherto, for the sake of simplicity, directed your attention 

 solely to the action, whether immediate or remote, which is exercised 

 by lime upon organic matter supposed to contain no nitrogen. Its action 

 upon compounds in which nitrogen exists is no less beautiful and simple, 

 perhaps even more intelligible and more obviously useful to vegetation. 



There are several well known facts which it is here of importance 

 for us to consider — 



1°. That the black vegetable matter of the soil always contains ni- 

 trogen. Even that which is most inert retains a sensible proportion of 

 it. It exists in dry peat to the amount of about 2 per cent, of its weight, 

 and still clings to the other elements of the organic matter, even after it 

 has undergone those prolonged changes by which it is finally converted 

 into coal. Since nitrogen, therefore, is so important an element in all 

 ^^egetable food, and so necessary in some form or other to the healthy 

 gr?wth and maturity of plants, it must be of consequence to awaken 

 this element of decaying vegetable matter, when it is lying dormant, 

 and tt cause it to assume a form in which it can enter into and be- 

 come useful to our cultivated plants. 



2^. Thu,t if vegetable matter of any kind be heated with slaked lime, 

 the whole of the nitrogen it may contain, in whatever state of combina- 

 tion it may previously exist, will be given off in the form of ammonia. 

 The same takes place still more easily if a quantity of hydrate of potash 

 or of hydrate of soda be mixed with the hydrate of lime. Though it 

 has not as yet been proved by direct experiment — yet I consider it to be 

 exceedingly probable, that what takes place quickly in our laboratories^ 

 at a comparatively high temperature, may take place more slowly also 

 in the soil, and at the ordinary temperature of the atmosphere. 



3°. That when animal and vegetable substances ai^ mixed with 

 earth, lime, and other alkaline matters, in the so-called nitre beds, (Lee. 

 VIII., § 5,) ammonia and nitric acid are both produced, the quantity of 

 nitrogen contained in the weight of these compounds extracted being 

 much greater than was originally present in the animal and vegetable 

 matter employed (Dumas.) Under the influence of alkaline substances, 

 therefore, even when not in a caustic state, the decay of animal and ve- 

 getable matter in the presence of air and moisture causes some of the 

 nitrogen of the atmosphere to become fixed in the soil in the form of 



