vi.] LIME AS A MANURE. 51 



CHAPTER VI. 

 NATURAL MANURES. 



94. Lime ranks as one of the most important 

 manures at the farmer's command, and its use dates 

 from very early periods of time. It exists very abun- 

 dantly in many of our rocks, as in our limestone and 

 chalk formations, in the form of carbonate of lime, 

 which is a compound of carbonic acid and lime. It 

 is also found in rocks as sulphate of lime, or gypsum, 

 which is a compound of sulphuric acid and lime. In 

 this form it is far less abundant than as carbonate of 

 lime. There is another supply of lime found in com- 

 bination with phosphoric acid as phosphate of lime, 

 but this exists in a still more limited quantity. This 

 is however a very valuable manure, and is carefully 

 sought for, wherever it can be easily raised and con- 

 veyed to a port for shipment. In the West Indies, 

 Spain, Portugal, Germany, Carolina, &c., very large 

 quantities are raised, and sent to England for the 

 manufacture of manures. Considerable quantities 

 are obtained in England, in the form of coprolites ; 

 but the present supplies are inferior in character to 

 those at first raised, and they scarcely compete with 

 the foreign supplies of high-quality phosphate of lime, 

 which are now so largely used. 



95. The use of lime as a manure is practically 

 limited to the employment of various forms of car- 

 bonate ot lime, either in a natural or prepared 

 condition. It is true that in combination with 

 sulphuric acid and phosphoric acid it is added to 

 the soil, but the sulphate of lime and the phosphate 

 of lime so employed are used for the sulphuric and 

 phosphoric acid they contain, rather than for their 

 lime. The carbonate of lime must be regarded as the 

 source of the lime used for the purpose of manure. 



