112 JOUENAL OF THE ROYAL HORTICULTURAL SOCIETY. 



less directly affected by variations in the temperature of the atmosphere 

 than by rain and snow percolating into the ground. The transference of 

 heat to the soil by conduction is a process which can proceed only very 

 slowly, whereas cold water percolating its surface will affect its tempera- 

 ture very readily ; the efitect of wind also in causing evaporation from this 

 surface, and so lowering the temperature, is also no doubt very consider- 

 able. 



In the same way the humidity of the air and the amount of rainfall 

 are important factors to consider, and they ought doubtless to be com- 

 bined with the temperature if we would arrive at precise results ; but the 

 consideration of all these I must reserve for some future occasion, if I 

 am honoured with another opportunity of bringing the subject of the 

 relation of meteorology to the phenomena of horticulture before the 

 Fellows of this Society. 



