HOWARD AND HOWARD 25 
holes }” in diameter on its side every half-inch apart up to a length of 6” from 
the sharpened end, was driven firmly into the soil at an angle of about 30°, 
so that the end of the tube penetrated to a depth of about 12” from the surface. 
Three inches of the tube remained outside the soil. The open end of the 
tube T outside the soil was connected by means of a rubber stopper R and a tap 
Fic. 5.—Apparatus used in determining the amount of carbon dioxide in the soil 
atmosphere. 
U toa capillary tube V to a Reiset’s apparatus A, containing a measured volume 
of baryta water of known strength. The Reiset’s apparatus was connected to a 
15 litre aspirator bottle B filled with water. The aspirator bottle was grad- 
uated by means of a paper scale to $ litres. Soil gas was aspirated through the 
apparatus by allowing the water to flow by means of the exit tube C attached 
