98 APPENDIX. 



No. 6 is the common oval drain, de 

 signed and adapted for very wet lands, or 

 for lands where only a slight fall can be 

 obtained. 



27. All fertile soils contain gypsum. 

 Sometimes it exists in sufficient quantity 

 for all the purposes of successful agricul- 

 ture, without any artificial supply ; and 

 in localities near the sea-coast the sulphate of soda sup- 

 plies its deficiency, if any exists. But where gypsum is 

 naturally abundant in the soil, it is profitably scattered 

 over the manure-heap, the stable, and the urine-tank, 

 for the purpose of arresting the escape and loss of the 

 volatile ammonia, which it transforms into the sulphate, 

 which is not volatile. Scattered also on corn and potato 

 drills, it is very serviceable in arresting the ammonia 

 which a spell of dry weather causes to ascend from the 

 manure beneath the soil, and in the form of the sulphate, 

 retaining it at the surface, ready to be again carried 

 into the soil with the first rain which falls. 



28. A knowledge of the chemical constituents (the 

 principal organic elements) which enter into the com- 

 position of urine, is of much practical value to the scien- 

 tific farmer. 



Carbon, 20.0 

 Hydrogen, 6.6 

 Oxygen, 46.7 



Nitrogen, 26.7 



100.0 

 In the process of decomposition this substance unites 



