Investigations JRegarding Brack'' {Alkali) in Gajje Colony Soils. 141 
neighbourhood of the 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 expected, 
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 ,, 
Magnesium sulphate 37'21 ,, 
Calcium sulphate 10*86 ,, 
Calcium carbonate Trace 
Of the alkaline salts that present in largest amount is sodium 
chloride, and the magnesium compounds exceed those of calcium in 
quantity. In the absence of sufficient lime this magnesia may prove 
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 "OlO '020 ,, 
Here, too, it will be seen sodium sulphate prevailed.! 
In a sample of water, taken from a pit on the site of the proposed 
dam, the total dissolved salts amounted to 50*40 grains per gallon ; of 
these salts the following are the principal ingredients : — 
* See Storer, " Agriculture in some of its Eelations with Chemistry," vol. ii., pp. 518 
and 519. 
t From the farm Culmstock, in the Division of Miclclelburg, and lying about 20 miles 
south of Thebus, a sample of efflorescence, 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 ,, 
Sulphur trioxide 33-8 ,, 
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, 
