EXPERIMENT STATION BULLETINS. 649 



the calculation of the preceding results. The first ten columns of table 

 11 show the actual pressure in atmospheres of mercury that the experi- 

 mental soils produced, and the last seven columns represent the same 

 data reduced to the basis of one-half cubic foot of soil, the percentage of 

 pore space in the experimental soil being taken as a basis. 



With these explanatory remarks in mind, the discussion of the data 

 may now be undertaken. Disregarding for the present table with the dry 

 soils, and considering only table 10 with the moist soils, it will he found 

 that temperature exerts a great influence on the aeration of soils. The 

 quantity of gas that would actually be exhaled or inhaled by raising the 

 temperature of the upper half cubic foot of soil from 0° to 10° C, 

 amounts to 326.2 cc. in the quartz sand, 288.8 in sandy loam, 325.7 in 

 silt loam, 354.0 in Clyde silt loam, 363.2 in clay, and 465.9 in peat. These 

 volumes increase very regularly and markedly with rise in temperature 

 so that at the temperature elevation of from 40° to 50° C. they amount 

 to 549.5 cc. in quartz sand, 559.0 in sandy loam, 567.6 in silt loam, 596.3 

 in Clyde silt loam, 605.3 in clay and 792.0 in peat. It must be noted that 

 this increase in volume with a rise in temperature is contrary to the law 

 of Charles which states that ''providing the pressure remains constant 

 the volume of a gas will change 1/273 for each degree of change of tem- 

 perature." In the present case the pressure, which is the atmospheric, 

 remained constant throughout the duration of the experiment. Accord- 

 ing to this law the results should follow the formula V = Vq (1 + at) in 

 which Vo represents the volume of the gas at 0° and V the volume at a 

 temperature of t and a = 1/273, so that the increase in volume for every 

 rise of 10° C. should be the same for all equal temperature increments. 

 The last column to the right shows the theoretical increase in volume 

 of air contained in the total pore space of the upper half cubic foot of 

 soil, for every rai.se of 10° C. up to 50° C. By comparing this theoretical 

 increase in volume with the actual increase obtained at the different 

 temperature elevations, the remarkable fact becomes at once evident that 

 the latter not only rises with every increment of temperature, while the 

 former remains the same, but also the difference between the two is very 

 marked even at the temperature elevation of from 0° to 10° C, and that 

 it is gradually accentuated with further rise in temperature so that at 

 the temperature elevati<m of from 40°-50° C. it is, in most cases about 

 4 times greater than that at 0°-10° C. For example, at the temperature 

 elevation of from 0° to 10° C, the difference in volume increase between 

 the actual and theoretical is 90.6 cc. for quartz sand, 38.8 for sandy 

 loam, 82.0 for silt loam, 78.0 for Clyde silt loam, 102.2 for clay, and 

 265.5 for peat. While at the temperature elevation of from 40° to 50° 

 C. the dift'erence is 314.1 cc. for quartz sand, 309.0 for sandy loam, 323.9 

 for silt loam, 320.3 for Clyde silt loam, 344.3 for clay and 592.6 for 

 l>eat. It will also be seen that the increase in volume of the actual re- 

 sults is 50 per cent greater from the rise of temperature of from 40° to 

 50° C. than that from 0° to 10° C. while the increase in volume of the 

 theoretical results is the same at both increments of temperature. 



The horizontal line to the left headed "emj)ty tube" contains some 

 very important information in connection with what has been said 

 above. This column contains the increase in volume of the air enclosed 

 in an empty tube of exactly the same capacity as that contained the 

 soils. The air in this tube was dried by heating the tube to 100° C. and 

 then cooling it gradually to 0° C. and allowing air to pass either through 



