Part 4-.] Center: Note on Rek or Alkali Soils and Saline JFell tvalers. 2G1 
magucsiau cai-bonatc held in solution by free carbonic acid. There is present 
probably next in amount soluble salt of lime and magnesia, sulphate or chloride— 
the maguosia iu smaller amount. The alkaline chloride, though the most con- 
stant ingredient in all waters, is in small amount, from ^ grain to 2 grains, and 
the alkaline sulphate in about equal or larger quantity. In the majority of well 
waters in the plains in my experience there is high permanent hardncs.s, indicat¬ 
ing lime or magnesian sulphate or chloride, and sodium carbonate is deficient. 
The total dissolved salts is in fresh well waters about double that in rivers and 
canals, and may rise in saline wells from 10 to 40 times the amounts, the 
increase being chiefly iu carbonate of lime and alkaline chlorides and sulphates.' 
The second group of waters or solutions is that containing carbonate of soda. In 
these there is generally little permanent hardness, or soluble lime or magnesian 
salt. If these two groups on evaporating produce cfflorc,sconce, in the first wo 
may have sodium chloride and sulphate, and any magnesian sulphate, if present; 
in the second we may have sodium carbonate with sodium sulphate and chloride, 
but no lime or magnesian salt. During the process of drying, which leads to tho 
efflorescence, tho first thing that occui’s is the deposition of lime and magnesian 
carbonate, as the free carbonic acid disappears. Subsequently, sulphate of lime 
being only little soluble would deposit, and the highly soluble salts, including 
sodium carbonate, chloride and sulphate, magnesium and calcium chloride and 
nitrate and magnesium sulphate, would be capable of efflorescence. These salts, 
however, are not deposited as they exist in solution, as now laws come into play- 
The chief of these is, that during evaporation the least soluble salt that can be 
formed is first deposited; but this is modified by two other law's, the tendency of 
certain compounds to form double salts, and the tendency of substances with the 
same crystalline form to crystallize out together. The efflorescences thus produced 
consist of three groups ; Isf, the neutral, containing no cai’bonato of soda, consist 
chiefly of sodium chloride and sulphate, and frequently magnesium sulphate; 2ud, 
tho alkaline, containing carbonate of soda and alkahno chlorides and sulphates, 
but no lime or magnesian salt; 3rd, the nitrous efflorescences. These generally 
contain no alkaline carbonate, and consists chiefly of nitrate of lime and alkaline 
chlorides. Others contain alkaline niti’ate, chloride, and sulphate. They are 
developed where the soil has become loaded with organic nitrogenous matter. 
In several places about Lahore there is a good deal of magnesian sulphate, and I 
have observed on twigs of farash trees a saline coating of this salt, Reh is thus 
not a special salt or mixture of salts, but a very variable compound. It is really 
the most easily soluble salt in the earth-W'atcr, remaining in solution after the 
deposition of carbonate of lime, &c., on evaporation. The ingredients and their 
relative proportions arc found to vary' in different places, exactly as tho W'cll 
waters at different spots differ in saline contents, and in the same area there is a 
'Though we speak usually of individual salts existing in a solution, this is not, strictly speak¬ 
ing, scientifically correct. If, for example, sodium chloride .and lime sulphate he ninde into a 
solution, it wiU really contain quantities also of sodium suliihate and lime chloride, and tho 
amounts of the four salts will depend on the masses of the first two, temperature, concentration, 
&c. Properly speaking, iu recording an analysis, the total amount of acids and bases should he 
separately recorded. By a eouveutioual rule, however, it is customary to arrange the salts hypo 
thetically. 
