96 



APPENDIX. 



When we speak of the sulphate of soda, we mean a 

 substance called a salt, composed of soda, which is 

 called the base, and sulphuric acid. Hence, the 

 phosphate of lime is a salt containing lime, the base, 

 and phosphoric acid ; and carbonate of potash, a salt 

 containing potash as the base, and carbonic acid. 



25. In addition to the four elementary bodies, carbon, 

 hydrogen, oxygen and nitrogen, which constitute the 

 organic part of plants, some of them also contain 

 small quantities of sulphur, and larger quantities of 

 phosphorus. These additional organic elements are 

 obtained from the sulphuric acid and phosphoric acid 

 contained in the soil. 



Sulphuric acid is a combination of sulphur and oxy- 

 gen. The plant decomposes the acid, retaining a por- 

 tion of its sulphur, and throwing off the oxygen with 

 which it was combined ; and the same explanation may 

 be applied to the phosphorus some plants contain. 



26. Reference has been made to under-draining wet 

 lands; we annex the methods whereby this result may 

 be attained. 



Good drains may be made with small stones, as shown 

 in the annexed sectional, 

 diagrams. They are very i 

 effective if well made, but 

 not so useful or durable 

 as those constructed of 

 tiles. The small stones 

 should be covered by a 



