ns ON MANURE 



combine with the alkalies in the soil, especially with lime, and a 

 soluble salt would thus be produced, which is known to possess a 

 favorable action on the growth of plants. This salt (muriate of 

 lime, or chloride of calcium) is one of those compounds which 

 attract water from the atmosphere with great avidity, and retain 

 it when absorbed ; and being present in the soil, it would decom- 

 pose the carbonate of ammonia existing in rain-water, with the 

 formation of sal-ammoniac and carbonate of lime. A solution 

 of bones in muriatic acid placed on land in autumn or in winter, 

 would therefore not only restore a necessary constituent of the 

 soil, but would also give to it the power of retaining all the am- 

 monia falling upon it in the rain for a period of six months. 



The ashes of brown coal and of peat contain frequently silicate 

 of potash, so that these might furnish to the straw of the cereals 

 one of its principal constituents ; these ashes contain also' 

 phosphates. 



ft is of much importance to the agriculturist, that he should 

 not deceive himself respecting the causes which give the peculiar 

 action to the substances just mentioned. It is known that they 

 possess a favorable action on vegetation ; and it is likewise cer- 

 tain, that the cause of this is their containing a body, which, inde- 

 pendently of the influence exerted by its physical properties of 

 porosity and capability of attracting and retaining moisture, as- 

 sists also in maintaining the vital processes of plants. But if the 

 subject be treated as an unfathomable mystery, the nature of 

 their influence will never be known. 



In medicine, for many centuries, the mode of action of all reme- 

 dies was supposed to be concealed by the mystic veil of Isis ; 

 but now these secrets have been explained in a very simple man- 

 ner. An unpoetical hand has pointed out the cause of the won- 

 derful and apparently inexplicable healing virtues of the springs 

 in Savoy, by which the inhabitants cured their goitre : the water 

 was found to contain small quantities of iodine. In burnt sponges 

 used for the same purpose, the same clement was also detected. 

 The extraordinary efficacy of Peruvian bark was found to depend 

 on a small quantity of a crystalline body existing in it, viz. 

 quinine ; and the causes of the various effects of opium were 

 detected in as many different ingredients of that drug. 



