44 



The AtiiKixiilicrf of the Suit 



II. The soil of the Rothamsled fiekh. 



All the samples of air dealt with in this paper hase lieeii iliawii 

 riom the Rothanisted fields. The soil is a heavy loam with many 

 stones: it becomes very sticky when wet, but can be <iot into a j;ood 

 crumbly tilth as it becomes drier. Its mechanical analysis is as follows: 



Top '.» inches. 



Name of fraction 



Diameter of particles | Broatlbalk % 



Hoos Field % 



Fine gravel 

 CV)arse sand 

 Fine sand . . 

 Coarse silt. . 

 Fine silt . . . 

 Clay 



3 to 1 mm. 



1 to 0-2 mm. 

 0-2 to 004mm. 



004 to 001 mm. 

 001 to 0002 mm. 

 less than 0002 ram. 



1-9 



6-2 



21-4 



:i2-5 



13-8 

 17-li 



20 

 6-8 

 19-6 

 28-9 

 16-5 

 18-8 



Summary and Conclusions. 



1. The free air iu the pores of the soil to a depth of G inches is 

 very similar in composition to the atmospheric air but it ditTers in two 

 respects : 



(a) It contains more COj and correspondingly less o.xygen, the 



average in 100 volumes being 0-25 volume COg and 20-6 of oxygen 



against 0-03 volume COj and 20-9f) oxygen in atmospheric air. 



(6) It shows greater fluctuations in composition. 



Usually the sum of the CO, and oxygen is only slightly less than in 



atmospheric air but at ]ieriods when nitrates rapidly increase there is 



