248 FERTILIZERS. 



may appear to have been lost ; still there is no occasion, really, to anticipate such a result, inas- 

 much as no vegetable grows without consuming them. It is, perhaps, a matter of time. It is 

 only upon lands which have been half worn or exhausted, that fertilizers show their immediate 

 value and power. On those lands which contain a tolerable supply of lime, the addition of this 

 substance is not seen in the crops ; still no one can doubt but that the land will wear longer 

 for this addition, or in other words, so far as the lime is required, its natural stock will last 

 longer for the addition. To a certain extent, marl and crushed shells of a sea beach may be 

 substituted for the more expensive phosphates. 15oth fresh water marl and marine shells con- 

 tain phosphates : they undergo a slow change in the atmosphere and become brittle ; but still 

 they should be broken, in order to favor a more rapid disintegration. That this change is slow 

 is proved by the fact that oyster shells, in large beds, which were raised above the ocean long 

 ago, remain entire and perfect. This is witnessed in numerous places. It is by the solvent 

 power of carbonic acid that the phosphates are dissolved and brought to a condition suitable for 

 the absorption by the roots of plants. 



JYitrate of Lime. Whenever animal and vegetable matters accumulate, they undergo decom- 

 position, and one of the results of the decomposition is the formation of nitric acid. Nitric acid 

 unites at once with lime and forms the deliquescent salt, nil rate of lime. When weeds and the 

 refuse of stables, intermixed with lime and earth, are put together in a compost heap, then this 

 salt forms, or is one of the products of the change which those mixed materials undergo. The 

 process is complicated. These substances contain nitrogen, and during the chemical changes, 

 nitrogen is liberated ; but in the act of disengaging itself from its old combination, it meets 

 with oxygen, and in this state of incipient freedom, called the nascent state, it forms this com- 

 bination with oxygen. To complete the formation of the salt, a base must be present. It will 

 unite with lime, soda, potash and magnesia, forming with these, their respective nitrates, all of 

 which are very soluble. 



Nitrate of lime is regarded as an active fertilizer : it succeeds better with some crops than 

 others. The charge against it is, that it increases the straw at the expense of the grain. 

 We should infer almost a priori that it would form a suitable top dressing for meadows, 

 where it is of course the object to increase the herbaceous part, and the .seed is of no conse- 

 quence. We should also be led to conclude that plants fed upon the nitrates would be richer 

 in nitrogen, than where they are left to obtain as they may, and under unfavorable circum- 

 stances, their ordinary food. The nitrates will not remain in the form they are taken up, they 

 rather undergo decomposition, and form the usual nitrogenous matters, albumen, casein, fibrin, 

 etc. Nitrate of lime has not been manufactured for agricultural purposes. It is probable that 

 its effects would be similar to the nitrates of potash (salt petre) and nitrate of soda The direct 

 application of this salt being unknown, in a measure, it will be passed by without farther re- 

 mark. 



Silicate of Lime. An insoluble salt, existing as it does, in combination with some rocks 

 and minerals, it will of course be found, to a certain extent, in soils, and probably, although 

 scarcely, in pure water ; the roots of plants, aided by carbonic acid, are competent to take 



