500 STATE BOARD OF AGRICULTURE. 



by means of which the water is heated. The bulb is connected to the 

 circuit breaker or magnet D which in turn is attached to the thermo- 

 stat E. F is a stirriniii: fan run by the motor G. H is a stand upon 

 which the soil box rests. This stand is brought as close to the tank 

 as possible and fastened to it by means of a wire, while the soil box 

 is pressed firmly against the side of the tank by means of the screw 1. 

 As soon as the box came in intimate contact with the source of heat, 

 records of the rate at which the heat traveled through the soil were be- 

 gun. The method adopted to measure this rate of heat transmission 

 was to note the time when the soil box was brought to the constant 

 source of heat also the time wlien the mercury colunm of each thermo- 

 meter began to rise. The bulb of the thermometer was always in tlie 

 center of the core or about 3 inches deep. 



