CONCLUDING REMARKS. 203 



of plants on heavy soils, and particularly on such 

 as consist of argillaceous earth. 



Ingenhouss proposed dilute sulphuric acid as 

 a means of increasing the fertility of a soil. Now, 

 when this acid is sprinkled on calcareous soils, 

 gypsum (sulphate of lime) is immediately formed, 

 which of course prevents the necessity of manuring 

 the soils with this material. 100 parts of concen- 

 trated sulphuric acid diluted with from 800 to 

 1000 parts of water, are equivalent to 176 parts of 

 gypsum. 



