DRAINING SOIL WAEMS IT. 139 



20 m. 



1 h. 30 m. 



2 h. 30 m. 

 12 h. 40 m. 



The mean temperature of the external air to ■which the box was 

 exposed during the above period was 42°; the maximum being 47° 

 and the minim.um 37°. 



ExPEEiMENT No. II. — With the same arrangement as in the preceding 

 case, a gallon of boiling water was introduced above the peat and 

 water, when the thermometer a was at 36° ; in ten minutes it rose to 

 40°. The cock was then turned for the purpose of drainage, which was 

 but slowly effected, and at the end of twenty minutes the thermometer 

 a stUl indicated 40°; at twenty-five minutes 42°, whilst the ther- 

 mometer 6 was 142°. At thirty minutes the cock was withdrawn from 

 the box ; and more free egress of water being thus afforded, at thirty- 

 five minutes the flow was no longer continuous, and the thermometer 6 

 indicated 48° The mass was drained and permeable to a fresh supply 

 of water. 



Accordingly another gallon of boiling water was poured over it 

 and in 



3 minutes the thermometer a rose to 77° 

 5 „ „ feUto76i 



15 j> J) J) 71 



20 „ ,, remained at 70^ 



Ih. 50 „ „ „ 70| 



In these two experiments the thermometer at the bottom of the box 

 suddenly rose a few degrees immediately after the hot water was 

 added; and hence it might be inferred that heat was carried down- 

 wards by the water. But in reality the rise was owing to the action of 

 the hot water on the thermometer, and not to its action upon the cold 

 water. To prove this, the perpendicular thermometers were removed. 

 The box was flUed with peat and water to within three inches of the 

 top ; a horizontal thermometer (af) having been previously secured 

 through a hole made in the side of the box by means of a tight-fitting 

 cork, in which the naked stem of the thermometer was grooved. A 

 gallon of boiling water was then added. The thermometer, a very 

 delicate one, made by Newman, was not in the least affected by the 

 boUing water in the top of the box. 



In this experiment, the wooden box is a field ; the peat and cold 

 water represent the water-logged portion; rain falls on the surface 

 and becomes warmed by contact with the soil and thus heated descends. 

 But it is stopped by the cold water, and the heat will go no further. 

 But if the soil is drained and not water-logged, the warm rain trickles 

 through the crevices in the earth, carrying to the drain-level the high 



