E. J. IJrS.SKLL AND A. APPLEYAHD 



39 



Appendix. 



I. Method of roUectivg and (oiah/tiijuj (he soil air. 



The apparatiis used for collecting the soil air is shown in Fig. 15 ; 

 it was used by Hall and Russell in their investigations of the air of 

 Romney marsh soils. It consists of a hollow cylindrical steel tube (A) 

 2 feet long, | in. outside and | in. inside diameter to which i,s w-elded 

 a side tube (R) 2i inches from the top to allow of the air being withdrawn 

 from the nozzle (S). The top of the tube is strengthened by a cap (B). 

 A solid cylindrical rod (A^) | in. in diameter with a flat side J in. wide 

 running its whole length fits tightly into the hollow tube ; it is provided 

 at the bottom with a collar | in. wide. 



Fig. 15. Apparatus fur the collection of soil air. 



To obtain a sample of soil air the tube is driven vertically down into 

 the soil to the required depth with a wooden mallet, great care being 

 taken to prevent lateral movements. The inner rod {N) is then punched 

 down about i in. and a rubber stopper {M) inserted in the hole at the 

 top of the tube. 



A -small bulb (0) of approximately 30 c.c. capacity provided with 

 a two way tap is connected to the side tube {R) by means of pressure 

 tubing, and also to a small mercury reservoir (P) ; it has a delivery 

 tube attached through which the gas is forced into a mercury trough 

 (W) for collection. The flat .side of the inner rod allows the gas to 

 pass fi-eely up the tube when the pressure in the bulb is diminished by 



