62 
METEOROLOGY OF 1 897. 
soil will carry heat down into the soil and raise the temper- 
ature in spite of the cooling effect of evaporation, so an ap- 
plication of colder water has the opposite effect and chills 
the soil, both by the direct abstraction of heat and from 
evaporation. 
§66. The diagram is here given because of its sugges- 
tiveness, and to call attention to the influence of the tem- 
perature of the water used. It also suggests a reason why 
most farmers find it undesirable to irrigate early in the 
spring and why fall irrigation is sometimes so advantageous 
irrespective of the need of moisture. 
The importance of considerations of this kind, illus- 
trated by the diagram, will be considered more extensively 
when the observations on irrigation and on soil temperature 
are published. 
