654 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



whilst the unseasonably cool nights of August and September are also 

 indicated in the curve of mean minimum (night) temperature. The 

 absence of low temperatures on the grass in October is shown by the 

 change in direction of the lowest curve in that month. 



Diagram 3. — During the early months of the year a fairly close agree- 

 ment is shown between the mean temperature of the air and that of the 

 soil at depths of one foot and two feet below the surface. Until May the 

 soil temperature lags somewhat behind that of the air, but from June to 

 the close of the year it is higher, and the less rapid loss of heat by the 

 soil during the autumn is well shown by the diagram. The range of 

 temperature in the soil diminishes with the depth, and in December the 

 sandy soil at Wisley was on the whole 2 degrees warmer at the depth of 

 two feet than it was at the depth of one foot, and degrees warmer at 

 four feet than it was at two feet deep. 



