ALKALINE SUBSTANCES, AND DECOMPOSES COMMON SALT. 4l0 



organic matter to those forms of decay in which acid compounds are 

 more abundantly produced. Hence, clay soils almost always contain a 

 portion of alumina in combination with organic matter. This organic 

 matter is readily given up to lime, and by the more energetic action of 

 this substance is sooner made available to the wants of new races of 

 plants. 



6°. I shall bring under your notice only one other, but a highly im- 

 portant, decomposing action, which lime exercises in soils that abound 

 in vegetable matter. In the presence of decaying organic substances 

 the carbonate of lime is capable of slowly decomposing common salt, 

 producing carbonate of soda and chloride of calcium. It exercises also 

 a similar decomposing effect, even upon the sulphate of soda, and, ac- 

 cording to Berthollet, (Dumas 7Vaite de Chemie, ii., p. 334.) incrus- 

 tations of carbonate of soda (of Trona or Natron, w^hich is a sesqui 

 carbonate of soda,) are observed on the surface of the soil, wherever 

 carbonate of lime and common salt are in contact with each other. 

 If we consider that along all our coasts common salt may be said 

 to abound in the soil, being yearly sprinkled over it by the salt sea 

 winds — that generally, along the same coasts, the application of 

 sulphates produces little sensible effect upon the crops, and that, there- 

 fore, in all probability they abound in the soil, derived, it may be, from 

 the same sea spray — we may safely conclude, I think, that the decom- 

 position now explained must take place extensively in all those parts of 

 our island which are so situated, if lime in any of its forms either exists 

 naturally or has been artificially added to the land. The same must be 

 the case also in those districts where salt springs occur, and generally 

 over the new red sand-stone formation, in which sea salt more especially 

 occurs. 



And if we further consider the important purposes which the carbo- 

 nate of soda thus produced may serve in reference to vegetation — that 

 it may dissolve vegetable matter and carry it into the roots— ^that it may 

 form soluble silicates, and thus supply the necessary siliceous matter to 

 the stems of the grasses and other plants — and that rising, as it naturally 

 does, to the surfhce of the soil, it there, in the presence of vegetable mat- 

 ter, provokes to the formation of nitrates, so wholesome to vegetable 

 life — we may regard the decomposing action of lime by which this car- 

 bonate is produced as among the most valuable of its properties to the 

 practical farmer, wherever circumstances are favorable for its exercise. 



§ 33. Action of lime on animal and vegetable life. 



It is only necessary to allude, in conclusion, to one or two other 

 useful purposes which lime is said to serve in reference to animal and 

 vegetable life. Thus 



P. It is said to prove fatal, especially in the caustic state, to worms, 

 to slugs,* and to many insects injurious to the farmer, and to destroy 

 their eggs and larvae. In Scotland it has been found in some instances 

 to check the ravages of the fly. On the other hand, in the state of car- 

 bonate, it is propitious to the growth of the land snail and similar crea- 



* Whon the wheat crop is attacked by slugs above ground, nofhinjj will do so much poos' 

 as slaked lime, sown over the crop before suniise. — Hillyard, Royal Agricultural Journa 

 iii , p. 302. 



