76 THE PHYSICAL PROPERTIES OF SOILS 



condition. If time will permit study also the effect of 

 organic matter upon the specific heat. 



The soils are heated in the oven to drive off the 

 hygroscopic moisture, and two 25-gram samples from 

 each are weighed out, one to be used for the deter- 

 mination of the specific heat of dry soil and the other 

 made up to 15 per cent of moisture for the determina- 

 tion on the moist sample. 



The sample under consideration is enclosed in a 

 bag of thin oiled paper and suspended, by a fine thread, 

 in the heater near a delicate thermometer. The steam 

 is turned into the jacket, and the soil is left in the 

 heater until a uniform temperature is reached. This 

 will require from one-half to one hour. Meanwhile 

 the calorimeter (E) is partly filled with water which 

 has stood in the room for a long time and has acquired, 

 as nearly as possible, th€ room temperature. The 

 quantity of water should be such that the water value 

 of the entire system shall amount to exactly 100 or 150 

 grams of pure water. 



A few minutes before the soil is brought into the 

 calorimeter the stirrer should be started, and the ther- 

 mometer read at frequent intervals. If the ther- 

 mometer shows a constant reading the calorimeter 

 is quickly brought under the heater, the sample 

 lowered into it, and the thread cut. The calorimeter 

 is removed as promptly as possible, the lid replaced, 

 and the soil thoroughly incorporated with the water 

 by the stirring apparatus. The thermometer is again 

 read at frequent intervals until the maximum is 

 reached, as indicated by a gradual fall in temperature. 



The specific heat is calculated by the following 

 formula, in which the loss in heat by the soil is 



