G. W. Robinson 383 



Calcareous volcanic ashes occasionally occur in the mountain area, while 

 in the sedimentary rocks only occasional thin bands of limestone are 

 found in the Silurian strata. Where soils have been given large dress- 

 ings of lime, as was formerly the case in Denbighshire, the loss of calcium 

 carbonate in the drainage accounts for its almost complete absence. 

 At Rothamsted about half of the rainfall finds its way into the drainage ; 

 in North Wales the proportion must be considerably greater on account 

 of the humidity of the atmosphere and the greater coolness of the 

 sumn^ers checking evaporation. With a rainfall of 40 inches per 

 annum in Wales probably 25 inches at least goes into the drainage. 

 The leaching out of soluble constituents must therefore be much 

 greater than it is in the drier districts of England and calcium carbonate 

 may be expected to disappear rapidly from soils under such high 

 rainfalls. 



It is remarkable that nitrates can be detected in most of the North 

 Wales soils in spite of the absence of calcium carbonate^. In any case 

 it would appear that a type of farming has been developed which dis- 

 penses with lime without any large apparent disadvantages. 



Determinations have been made of the lime requirements of a large 

 number of soils by the method of Hutchinson and McLennan. In most 

 cases the deficiency is greater than -2 % calcium carbonate. 



5. The high figures for organic matter are readily explained. On 

 the one hand the humid climate with its mild winters favours vege- 

 tative growth. On the other hand the aerobic decomposition of organic 

 matter in the soil is hindered by the absence of calcium carbonate and 

 the fact that during a large part of the year soils are very poorly aerated 

 consequent on the interstitial spaces of the soil being occupied by water. 

 These circumstances favour anaerobic changes, by which a "sour" 

 peaty humus is produced. 



6. The amount of potash in North Wales soils is generally rather 

 high when it is considered that clay soils are so rare. This is not how- 

 ever surprising, since it has been shown that the coarser fractions 

 contain so much unaltered rock and comparatively little quartz. It 

 is not certain whether these soils are benefited by potash manuring. 

 The average of a number of trials made in various parts of the area 

 for a number of years shows comparatively little return for potash 

 manuring. 



7. Phosphoric oxide in North Wales soils presents few points of 



1 The writer is indebted to Mr E. J. Roberts, research student of this college, for 

 observations on this point. 



