255 
PART 4.] Center : iVo/e on Beh or Alkali Soils anil Saline Well loaters. 
much greater proportions of the same salts. This water not only comes in con¬ 
tact with a larger quantity of degraded rock and washes out its soluble salts, 
hut it takes up more carbonic acid from the air in the pores of the ground, which 
is rich in this gas, and this dissolves more lime and magnesian carbonate. From 
10 to 26 grains per gallon arc found in S23rings in clean soils in various hill 
stations. In the hill stations themselves, where the porous subsoil becomes 
loaded with sewage imjmi'ity from human habitation, the dissolved salts and 
organic imjmrity may he very great. For example, in the bazar well at Murree 
I found 35 grains per gallon in which were 12 grains of common salt. This last 
is, however, a sanitary fact, and I wish at jiresent to speak generally of the saline 
ingredients washed out of such soils not contaminated by human occupation. 
6. The soluble substances produced by rook decomposition and dissolved by 
water are remarkably uniform in their nature, though varying in amounts, both 
relative and total, according to the nature of the decomposing rock or soil. It 
may he generally stated that the earth water shows a fugitive acidity from the 
presence of free carbonic acid and a slight permanent alkalinity from the pre¬ 
sence of alkaline carbonate, but that the main ingredients are carbonates of alka¬ 
line earths, chiefly of lime, and alkaline chlorides and sulphates, chiefly of soda. 
Other ingredients are generally in smaller amount, such as lime and magne.sian 
chlorides or suli^hates forming the permanent hardness, also silica, traces of iron, 
&c. Of course in si^ecial formations it may be highly charged with peculiar 
salts, and may oven form what are called mineral springs ; but wo are speaking 
generally of the body of water that filters from the hill-sides, and either sinks 
into the underground strata of the plains or finds its way into the streams and 
rivers, and thence into the sea, the great natural reservoir of the soluble salts 
washed out of the earth. The waters of the Punjab rivers which I have 
examined, the Ravi, Jhelum, and Indus, contain 8 to 15 grains per gallon, vary¬ 
ing according to the floods. The amount of soluble salt capable of eflloresceuce 
varies from about 2 to 4.j grains. The river waters are most concentrated 
when they are at the lowest. At that time they are .supidied by the water that 
has filtered through the soil and subsoil of the higher regions, and has thus taken 
up more salts. In the hot weather, when the glacial water comes down, and in 
the rain floods at the end of the hot season, the dilution is at its highest. Other 
glacial rivers and those subject to annual flood.s show the same thing. For 
example, the total solids in Nile water vary from 9| to 14| grains per gallon. 
6. To oxjjlain the ultimate origin of these salts we have to consider the action 
Ultimate origin of reh of tlio oxygen and carbonic acid in rain water on the rock 
salts. elements. AVith the exception of the limestone strata, 
which consist of carbonate of lime, often with carbonate of magnesia, all great 
rock formations arc composed of silica and silicate.s, chiefly of alumina, lime, 
magnesia, soda, and jiotash, with smaller amounts of iron and other metals. Such 
is the constitution of the granites, gneis.scs, slates, traps, &c. The old sedimen¬ 
tary rocks are similar in composition, being formed by the disintegration of these. 
The recent alluvia of the plains consist of finely-divided debris of the limestone 
and silicious groups, and in them the chemical decomposition going on under the 
influence of air and water is much intensified, owing to the state of fine division 
