EXERCISE A-29. TO SHOW THE INFLUENCE OF COLOR 

 UPON SOIL TEMPERATURE. 



Equipment: Box 4''X12''X24''; two thermometers; 

 chalk dust; soot or lampblack; twenty grains of corn. 



Method: Fill the box with moist soil and plant the 

 corn in regular rows. Scatter chalk dust over one-half 

 of the box and soot or lampblack over the other half to 

 the depth of a quarter of an inch. Insert the bulb of a 

 thermometer about one-half inch beneath the surface in 

 the middle of each half of the box. On the first day read 

 the thermometers every two hours from early in the morning 

 until two hours after sunset. Make a record of the num- 

 ber of corn plants which come up in each half, on the day 

 when they can first be seen. 



TEMPERATURE. 



PLANTS UP. 



61 



