EXPERIMENT STATION BULLETINS. 553 



ing between ilie surface soil and the snow prevents a very intimate 

 contact between the two and thereby cuts down tlie rapid loss of heat. 



DAILY AND MONTHLY RANGE OP TEMPERATURE. 



Mention has been made that the temperature of the different soil 

 types under discussion, was recorded three times a day, at 7 a. m., 12 

 m., and G p. m. At these i>eriods high and low temperatures were ob- 

 tained at all three depths. These temperatures are probably not the 

 absolute maximum and minimum. To obtain these it is necessary 

 either to take records very often or continuously- by means of thermo- 

 graphs or other conlinuous self recording instniments, because the 

 absolute maximum and minimum temperatures of the various soils and 

 of the different depths occur at different times. These low and high 

 temperatures as obtained tri-urnally in the present work, however, are 

 believed to be very close approximations to the absolute maximum and 

 minimum, and especially for the upper 6-inch depth, which of course, 

 for practical purposes, is the most important. The half-hour records 

 which were taken at various times for the heat conductivity measure- 

 ments, as well as the dailv tri-urnal r-ecords, show that as a general 

 rule the minimum occurred for the gravel and sand about 7 a. m., for 

 the clay and loam about 12 m., and for the jieat about 6 j). m. On 

 the other hand the maximum was attained for the gravel and sand 

 about G p. m., for the clay and loam a little later, and for the peat 

 about 7 o'clock the following morning. The difference from the regular 

 period to the time the highest or lowest reading was recorded is, there- 

 fore, not very large. 



These high and low, or maximum and minimum, temperatures for all 

 the different soils and for all three different depths are shown in the 

 following tables and diagrams. The tables contain the daily and month- 

 ly high and low temijerature for each soil and for each depth. On the 

 diagrams are plotted the differences or amplitudes of these maxima 

 and minima. The daily meteorological elements are also plotted and are 

 the same as in the foregoing charts, except the air temperature, in 

 which case the difference or amplitude is shown here instead of the 

 average as in the preceding charts. 



