144 



AGRICULTURAL REPORT. 



EXPERESIENTS TO 



DETERMINE THE INFLUENCE OF GROWING VEGE- 

 TATION ON TEMPERATURE. 



These •experiments were conducted vritli the thermo-electric ap])aratus 

 of Kuhmkorti". The needle was adjusted in each experiment so that its 

 zero indicated the temperature of the room, and the graduation of the 

 arc ga^•e 4.8° equal to 1° F. The experiments were commenced on the 

 29th of June, 1872. The signs + and — indicate a temperature above 

 or below that of the room. 



The above experiments, though not full enough to be condusive, in- 

 dicate that growing vegetation reduces temperature iu its vicinity, in 

 the ratio of the rapidity of the vegetative action. Whether this is to 

 be attributed entirely to the evaporation of water from the leaf, or to 

 other causes in conjunction, is a question yet to be determined. That 

 evaporation is "the chief cause of the reduced temperature is estab- 

 lished by the fact that leaves in which the stomata are closed deflect the 

 needle + , but still the elevated temiierature did not equal that of the 

 sunshine from which the leaves were taken. The greatest deflection 

 -f obtained from leaves was 15'°, while a sheet of white paper from a 

 sun-exposure gave 40°. As the formation of carbonic acid in the com- 

 bustion of wood gives out heat, so we would infer that the deoxidizing 

 of carbon in the function of the leaf would absorb heat. To determine 

 this point would require a series of experiments to ascertain accurately 

 the ratio existing between the reduction of temperature and the amount 

 of water evaporated. Our purx)ose in the present experiments was to 

 determine the effect of growing vegetation on the solar heat which it 

 receives. From these experiments we are satisfied that the solar rays 

 received by growing vegetation heat the atmosphere less than the 

 same rays received on the bare earth or on rocks. Therefore growing 

 vegetation mitigates summer heat, and to that extent influences cli- 

 mate. 



Several experiments were made during the month of August to de- 

 termine the difference between the temperature of the earth exposed to 



