1 O'> 



loo 



the level at which all the alkalies had chanced to be concentrated ; or, again, by 

 taking a sample of the 1st, 2nd and 4th feet, or of the 1st, 3rd and 4th feet, when, 

 i) wing to the capricious distribution, all of the salts had been collected in the 2nd 

 and 3rd foot, and thus were overlooked because it may have been thought not worth 

 while to make a complete section of the soil in question." 



An analysis was made of a sample of efflorescence from the soil in the 

 neighbourhood of the Thebus works, obtained by enclosing a quantity of 

 the soil, to a depth of several feet, with a metal cylinder, drenching the 

 soil with water, and allowing it to dry by exposure. As was to be ex- 

 pected, evaporation of the water led to the appearance of a layer of salts 

 on the surface, and this layer, on being scraped off, was found to have the 

 following composition : 



Sodium chloride 40'16 per cent. 



Sodium sulphate 11'64 



Calcium sulphate 10*86 ,, 



Calcium carbonate Trace. 



Magnesium sulphate 37'21 ,, 



Here, too, it will be seen that of the alkaline salts, that present in 

 largest amount is sodium chloride, and that the Magnesium compounds 

 exceed those of Calcium (Lime) in quantity. In the absence of sufficient 

 lime this magnesia may pro>ve harmful.* 



Two similar samples of efflorescence mixed with earth, collected by 

 Dr. Nobbs near the same spot, were analysed, with the following results : 



Total soluble salts 1'209 per cent. 1'495 per cent. 



Sodium chloride '058 ,, '491 ,, 



Sodium sulphate 1'122 '895 



Magnesium sulphate '048 ,, 



Magnesium carbonate '008 ,, 



Calcium carbonate '010 '020 ,, 



Here, it will be seen, sodium sulphate prevailed, f 



In a sample of water, taken from a pit on the site of tine proposed dam, 



the total dissolved salts amounted to 50'40 grains per gallon ; of these salts 



tEe following are the principal ingredients : 



* See Storer : Agriculture in some of its relations with Chemistry. Vol. II., 

 pp. 518 and 519. 



t From the farm Culmstock, in the Division of Middelburg, and lying about 

 twenty miles south of Thebus, a sample of effloresence, such as frequently occurs on 

 the surface of brack soils, was collected. Analysis showed it to contain, inter alia, 



Chlorine 7'8 per cent. 



Carbon dioxide 6'2 per cent. 



Sulphur trioxide 33 - 8 per cent. 



The salts present therefore consisted mainly of sulphates. In both these Divisions 

 (Steynsburg and Middelburg) there are extensive plains of Karroo veld, which, but 

 for the liability to brack, would answer excellently for irrigation and cultivation 



purposes. 



