106 NITRATE OF LIME. 



where they must have laid for centuries, that 

 bones taken from any of these sources, crushed 

 and applied to the land, are equally beneficial 

 in their results. 



Having thus established the presence of this 

 earth in plants, and its importance as a stimu- 

 lus, the next consideration is to explain its mode 

 of action ; and more difficulty exists in doing 

 this satisfactorily, than in any of the previous 

 substances that have been noticed. 



Phosphate of lime is described as an insipid 

 white powder, insoluble in water, but soluble 

 in dilute nitric, muriatic, and acetic acids, but 

 this does not . at all help to solve the question 

 as to how it is to dissolved in the laboratory of 

 nature. . It is supposed either that the salts and 

 gases which (page 70) are constantly present 

 in water, have a sufficient solvent power to 

 enable the plant to take up this substance, or 

 that the electricity which we know is always 

 present, during any change in the state of mat- 

 ter, and consequently always in action during 

 the germination of seeds and the growth of 

 plants, that this agent exerts an influence in 

 some way or other to allow of the solution of 

 this phosphate of lime in water. 



It is admitted at once and frankly that the 

 theory here set forth is liable to many objec- 

 tions, but so is the subject, and we are by no 

 means yet in a position to explain how the so- 

 lution and assimilation of this substance is 

 effected. 



Nitrate of lime, (nitric acid 66 parts, and lime 

 34 parts, ) exists also in a state of nature. There 

 it is formed by the nitrogen of decaying, ani- 



