4 
Of course all plants are not equally affected by salt. Salsolaceous and many 
coast plants seem to be benefited by comparatively excessive amounts, while others, 
such as ferns, are very sensitive to its action, and suffer with a slight excess. 
It is convenient, as saving the labour of calculation, to represent the salt by 
the amount of chlorine it contains. Salt consists of 35-5 parts bv weight of chlorine, 
and 23 parts of sodium ; and, in examining the water for salt, the most expeditious 
method is to estimate simply the chlorine in it, and to take this chlorine as an index 
of the amount of salt ; thus, 30 parts of chlorine per 100,000 would indicate approxi- 
mately 50 parts of salt per 100,000. In this report the results of analysis are entered 
simply as chlorine in parts per 1 00,000. 
And judging from the considerations above given as to the amount of salt 
used in ordinary farming, we may say that a water containing, as a usual thing, 
15 parts of chlorine per 100,000 may be safely used for irrigation ; that an average 
of 30 parts of chlorine per 100,000 is an outside limit for an open sandy or gravelly 
soil, where there is sufficient winter rain to wash away the salt which may accumulate 
during the summer; and that 50 parts of chlorine per 100,000 is the outside limit 
permissible, and that this amount should occur only occasionally. 
This point being decided, our attention was next given to the vertical 
distribution of salt in the river, so that we might be able to advise upon the 
possibility of obtaining sufficiently fresh water by taking from the surface only. 
For the purpose of this investigation it was not sufficient to take samples from only 
one point in the river, as for instance from mid-stream, since the conditions might be 
different near the bank ; nor was it sufficient to take samples simply from the top 
and the bottom ; for in case the water at the surface was found to be fresh and at 
the bottom salt, it would be necessary to ascertain to what depth the fresh water 
extended. It was necessary also to consider the possibility of local currents and 
eddies which might at times and in places carry with them streams of salt close up 
to the surface. And, finally, it was necessary to consider how far the vertical 
distribution of salt in the river might be affected by tides anil by falls of rain. 
In order that all these points might be properly tested, it was necessary to take 
samples in such a way as to represent complete sections of the river ; these sections 
to be taken periodically, at intervals to be decided by experience. It was decided 
first of all to take them on certain days at intervals of a week, and on each of these 
days to take them twice, namely, at high and at low tides. 
Description of Gathering Samples . — F or this purpose a rope long enough to 
stretch across the river was obtained, and divided, by convenient marks, into regular 
intervals. This being stretched across the river enabled those in charge of the boat 
to quickly fix themselves at the proper horizontal distances. For fixing upon the 
points in vertical depth, two light iron gas-pipes were obtained, a shorter and a longer 
one, to be used respectively for shallow and great depths. These were graduated 
into 6-in. intervals. A case for containing the bottle was screwed on to one end of 
the pipes. A simple arrangement was clamped on to the side of the boat, allowing 
the rod to be let down into the water through a vertical groove ; by this means the 
rod was easily held in a vertical position. The operation of gathering samples will 
be readily understood from the accompanying sketch. 
At the time of gathering samples by aid of the rope, two men Avere employed, 
one standing 100 yards above and the other 100 yards below the site, so as to warn 
boats to look out for the rope. 
It was not considered necessary for the purposes of this investigation to go 
deeper than 1 5 feet. The depths at first decided upon Avere as follows : — 
At A, Mid-stream. 
At B and B l , 
About zo feet from A. 
At C and C 1 , 
At D and D 1 , 
About 1 3 feet from Bank. 
3 feet from Bank. 
Surface 
Surface 
Surface 
Surface 
6 inches deep 
6 inches deep 
1 foot deep 
1 foot 
1 foot „ 
1 foot „ 
2 feet „ 
Bottom 
2 feet „ 
2 feet „ 
3 99 99 
3 99 99 
5 99 99 
10 » 
*5 „ 
3 9 ) 99 
5 99 99 
10 » » 
Bottom 
