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annually by the rain. Of ammonia 2 to 10lbs., and of sulphuric 
acid 10 to 20lbs. are added from the same source to every acre of 
land in localities favoured with a fair amount of rain. 
Of stream water some prove better than others when used for 
irrigation, and they vary according to the amount of substances 
they carry either in solution or in suspension. 
Well water is, as a rule, even more highly mineralised than 
stream water, and is often injurious to vegetation, especially in the 
Eastern and inland districts, where it is not infrequently unfit for 
consumption. 
Taste is the readiest means of ascertaining whether water is 
fit for domestic or irrigation use. 
A erystal clear well water often proves worthless for irrigation 
purposes, whereas a spring or a well well-stocked with, acquatic 
plants and luxurious vegetation, and where stones at the bottom 
are covered with green slime, always holds water fit for irrigation. 
The best indicator of the fitness of water for irrigation is the 
palate, and when the taste is decidedly mawkish it is advisable to 
have a sample analysed before going through the trouble and the 
cost of providing for its lifting and cost of distributing it on the 
ground. An analytical statement is often perplexing until the array 
of figures is understood. 
In water analysis the residue or solid matter either held in 
suspension or in solution is expressed in so many grains per 
gallon, or so many parts in 10,000 parts. We have seen in a 
previous chapter when dealing with manures that the weight of 
one acre of agricultural soil one foot deep is approximately 
3,500,0001bs. It has, moreover, been determined by chemical 
investigation that a soil containing -1 per cent. of soluble salt is 
unsuitable for cropping, and is only fit for growing salt-loving 
plants. 
The question, therefore, which the irrigationist has to solve 
is: What amount of water containing a given quantity of salt will 
be necessary to cause the accumulation into the ground of approxi- 
mately .1 per cent. of salt (equivalent to 3,500lbs. to one acre one 
foot deep) ? 
That question, indeed, can only be approximate, as a certain 
proportion of that saline matter would be leached out of the 
ground during the rainy season; sandy soil could, besides stand 
more salt than the more retentive soils, such as loam or clay, 
and drainage would also delay to some extent the period when that 
dangerous point of -1 per cent. of salt would be reached. When 
calculating the amount of salt added to the soil by water contain- 
ing a known number of grains of that substance to the gallon, it 
must be borne in mind that one gallon contains 7,000 grains. As 
1 inch of water over 1 acre is equivalent to 22,630 gallons (101 
