Practical Expci'iments on the Air-drainage of Land. 
341 
two feet deep and five 3ards apart, each discharging into a 
covered outfall at the bottom of the field. 
In the autumn of 184G it occurred to me that this, being a 
shallow-drained field, presented a good opportunity for experi- 
ment ; I divided it into five compartments, each containing five of 
the drains. With the two outside and centre compartments T did 
not interfere. Into the two other compartments I introduced 
what I call an air-drain across the upper ends of the five drains 
in each case, to join them together. I then connected the air- 
drain so cut with the adjacent open ditch at the top of the field, 
in order to increase the natural current or circulation of air 
through the ordinary drains. 
The following diagram may serve better to illustrate my case : — 
The black lines represent the Fences ; the flatted lines the D7-ains ; the complete lines the 
Air-drains. 
Air. 
Discharge. 
The field was afterwards cultivated in the usual manner for 
turnips, and I did not again visit it until Wednesday the 19th of 
May, 1847, the very heavy rains of the winter and spring having 
concluded late the previous evening by a pouring rain of four 
hours' duration ; Mr. Stafford and I on this day traversed the field 
in all directions, and the superior condition of the soil on the 
two air-drained pieces was everywhere distinctly apparent ; but 
what afforded proof more convincing and undeniable was the 
circumstance that, on ploughing the field across all the drains, 
on the following morning (Thursday), wet bright marks were left 
by the plough on the land within the two outside and the centre 
compartments, but no indications of wetness appeared on the two 
air-drained pieces. 
We together again visited the field on the following 4th of 
August, when w^e found the turnips, owing to the intervening and 
