150 



Ague'and fever are principally caused by the noxious exhalations evol- 

 ved from stagnant water, during its evaporation by the solar heat. The 

 Deanston_,sy8tem seems to be best adapted to the soil of Michigan, and 

 ifc will no doubt, be brought into general use in this State. 



The following cut represents a field drained according to this sys- 

 tem: 



A 



In this cut a. a. a., denote the fences, h. h. h. the main drain, c. the 

 outlet,/././ the water, falling from the centre of each interval into 

 £be minor drains, g. g. g. are slight turns given to the small drains, at 

 tlieir junction with the main drain ; these turns are given in the direc- 

 tion of the current, in order to prevent the water from running out too 

 rapidly against the sides of the main, and thereby causing obstructions 

 by depositing sediment, &c. 



The parallel drains run up and down the declivity, instead of across 

 the slope or inclination of the ground, as was the case in the old sys- 

 tems. In the Deanston plan, the water runs from the centre of each 

 space into the drains, in the old system it falls only from one side of 

 each space, and sometimes from one drain into another. 



The drawing represents the Deanston system in its simplest form, it 

 will be easily understood that in large plains, and in uneven ground, 

 several sub-mains will be necessary, and these must be judiciously 

 placed. The small drains must not he of too great a length, lest the 

 quantity of water become too great for them to carry. The length of 

 the small drains, and the dimensions of the main and sub-mains must 



