26 TROPICAL AGRICULTURE chap, hi 



And, in the same way, the soda, in a soda double silicate, 

 will be given up for lime or potash or ammonia ; and the 

 lime, in a lime double silicate, will be given up for potash 

 or ammonia, if these substances be brought near to it. This 

 property of the double silicates is most important to the 

 agriculturist, and it has been made of much use in the 

 system of applying artificial manure to land. 



