258 
llecorch of ihe Geological Survey of India, 
[vOL. XIII. 
pulverising the soil and acting on it by water. In countries with good surface 
and underground drainage there is a constant escape of these salts, and the 
difficulty may bo how to got enough of them. In many parts of our plain.s 
circumstances favour their accumulation, and the question is how to get rid of the 
excess. I have frequently taken samples of soil and subsoil from places where 
there were efflorescences and where there were none, and on washing out the 
soluble substances with boiled distilled water found that they were similar, but 
different in amounts. They always consisted chiefly of alkaline chloride and 
sulphate, with often small quantities of alkaline carbonate, and frequently larger 
amounts of soluble magnesian salt, sulphate or chloride. Another experiment 
was to take a sample of reh soil and wash it repeatedly till no trace of soluble 
salts could be found. It was then dried and thoroughly mixed and a portion 
tested again to see that no soluble salt was present. It was then placed on a 
filter and covered with porous filter paper so as to exclude dust, but allow 
evaporation, and the bottom of the glass filter was coi-ked. It was frequently 
watered with distilled water charged with carbonic acid and exposed to the 
heat and light of the sun in the hot weather for nearly three months. At tbe 
end of that time it showed no efflorescence, but on being washed with distilled 
water the solution showed tbe presence of considerable quantities of alkaline 
chlorides and sulphates. This experiment proved that in that .sj)ecios of soil 
a sensible production of reh salt may take place in a few months. A similar 
sample irrigated with ordinary well water rapidly developed an efflorescence 
owing to the presence of salts in the water. There is nothing particularly novel 
in these results. Experiments have often been made of grinding down the solid 
rock from the debris of which the adjoining country was formed. On washing 
out the powdered rock the solutions were found to contain the salts of the water 
of the district; indeed it is always possible to account for the composition and 
proportions of the ingredients in a water draining any area if the structure and 
composition of the rocks are known. 
13. To estimate approximately the decomposability of a soil, the simplest 
. . , ,. . method is to dry and weigh a sample and wash out from 
Apiiroximatc estimate “ “ , V, n ■ i ■ , 
of decomposition in soils: it the soluble salt already present. On drying and woigh- 
tlie Lysimeter. jjjg tjjg residue and deducting its ■weight from the original 
there will be found the soluble salt (along with some organic matter). This is 
the result of decomposition already accomplished. The solution may bo tested in 
the usual way, by evaporation to find the total dissolved matter, and by ignition 
to find organic matter. The washed residue of earth is then ignited to expel all 
I'cmaining organic matter, and treated with hydrochloric acid, which will decom¬ 
pose and dissolve the materials which are in an easily decomposable state, The 
solution -will contain lime, magnesia, alumina, and iron, and also the alkaline bases 
capable of efflorescing. On deducting the undissolved residue from the former, 
a figure will be found, -which will be an approximate index of the facility of 
decomposition of the soil. The hydi-ochloric acid solution can be examined in 
the usual way if required by first precipitating the iron, alumina, and jihosphates 
of the alkaline earths, then the lime, and afterwards separating the magnesian 
and alkaline bases. The last will show the salt capable of efflorescing. A more 
