182 



There is a general resemblance between the soils K and M, the former 

 being an improvement on the latter. The worst kind of brack, sodium 

 carbonate or black brack, occurs in the soils L, N, and P. At L it makes 

 its appearance at the fourth foot, at N it rises to the third, and in larger 

 proportions, while at P it appears at the surface and averages in amount 

 from two to three times that in the corresponding levels at N. 



It will be noticed that the Magnesium salts exceed on the whode the 

 lime salts in quantity, and here may be said, what does not appear from the 

 figures already given, that the soils K and M show a small proportion of 

 the rather undesirable Magnesium chloride in the first couple of feet. 



The amounts of alkaline carbonates in the Thebus samples are lower 

 than in the soils of the Tulare Experiment Station, California, as reported 

 by Professor EQlgard, and the alkaline salt present in largest proportion 

 is sodium sulphate, at K, and sodium chloride at the other points where 



Character of Alkaline Soil at Zoutkuil, Thebus. (The truncated mountains in the - 

 background are Thebus and Koffiebus.) 



samples were taken, but then the Tulare Station may be taken as repre- 

 senting an extreme case, and there is no saying whether much worse in- 

 stances than the present may not be found at Thebus if a more complete 

 investigation be undertaken. 



It will be noticed how irregularly the soluble salts are distributed 

 through the soil; this irregularity is caused by the varying permeability 

 of the soil layers, and by the bands of gypsum which traverse the valley. 

 To this variability is due the peculiar nature of the results obtained by 

 analysis from the samples collected at Thebus, and numbered 10 to 19 (see 

 p. 127). These samples were evidently not typical, and may even, in some 

 cases, have been taken out of the very bauds of gypsum just mentioned, 

 henoe their abnormal percentages of lime. Irregularities of this type are 

 of common occurrence in alkali soils : King (Irrigation and Drainage, 

 page 283) states that 



"in examining soils for alkalies, it is a matter of the utmost importance to recog- 

 nise that the distribution of them is extremely liable to be capricious, and that it 

 is easy to overlook their presence by stopping the campling of the soil just short of 



