5 
The bottles, in addition to having been marked by means of a diamond, were 
arranged in proper order in a case with divisions in it; thus the possibility of error 
owing to the accidental mixing of the bottles was minimised. The bottles having been 
let down in the water to the proper depth, the india-rubber stopper was drawn by 
means of a string; the bottle was kept in its position until no more bubbles of air rose 
from it; it was then drawn up and replaced by an empty one. In this way it required 
from 35 to 45 minutes to gather the 38 samples representing one section. 
The sites selected for these sections were those marked 1, 2, and 3 in the 
accompanying sketch map, namely, at the present pumping house, near the old 
pumping house, and a little below the Botanic Gardens footbridge. 
Preliminary Examination . — Preliminary samples were taken on the 16th Decem- 
ber, at high and at low tide, at the present pumping station (No. 1), in mid-stream and 
about 13 feet from the left (south) bank. The results are given in Table I. It will 
be seen that the chlorine was in all cases above 30 parts per 100,000; that is to say, 
outside the limit which we had fixed upon as a safe average. It was considerably 
above that limit at a depth of 10 feet. In mid-stream, at shallow depths, it was a 
little less at high tide than at low, whereas at a depth of 10 feet it was considerably 
less at low than at high tide — a fact which seems to indicate that with the ebbing tide 
the briny under-current was drawn out to sea, and the fresh upper-current, by the 
commotion thus caused, became to a certain extent mixed with the under- current, and 
thus rendered salter. Near the bank, however, the water at shallow depths was less 
salt at low tide than at high, an irregularity similar to many others which were 
subsequently observed. Preliminary samples were again taken on the 1 8th December 
at high tide, and throughout indicated that the water was getting salter; at a depth of 
10 feet the water had already risen to 71 1 parts per 100,000. 
The first complete sections were taken on 24th December, and the results are 
given on Tables I., II., and III. From the 21st to 23rd December heavy rain had 
fallen, and it was anticipated that the water would be less salt than before ; neverthe- 
less, the results gained were very surprising, for they showed that at all the three 
sections the water was absolutely fresh down to the lowest depths. They demon- 
strated how rapidly at this early stage in the season the river could be swept clean by 
flood waters. 
Four days after this, namely, on the 28th, a sample was taken from the pump- 
ing house well, and showed that the chlorine had already risen to 30*6 parts per 
100,000. O11 the 30th December it was only 20*6, and on the 31st again 30*6. 
On the 2nd January the second complete sections were taken, but this time 
from only one site, namely, the present pumping station, since the taking of three 
sections had been found during the first trial to absorb more time than could be spared. 
Vertical Distribution. — T he results gained this time were interesting and 
instructive. They showed (vide Table I., 2nd January, low tide) that, whereas in 
mid-stream the chlorine was only 32*5, at the banks it averaged 50. Indeed, the 
fresh water current seemed to be concentrated within a breadth of 20 feet in the middle 
of the river. They also showed that at shallow depths the water was salter on the 
left side of the stream than 011 the right, though not very much so, the figures being 
51 on the left and 48*6 on the right. They showed that at a depth of 1 foot the water 
began to increase in saltness. They also showed the existence of minor local currents 
producing considerable irregularities in the distribution of the salt; for, whereas at the 
bottom (about 8 feet deep) at C, 13 feet off* the right bank, the chlorine was 840; at 
C 1 , the corresponding position on the left side of the river, it was less, viz., 59 2 ? 
but at B, midway between A and C 1 on the right side, and at B 1 , the corresponding 
position on the left side, the conditions were reversed, being less, viz., 7 66, on the right, 
and more, viz., 920, on the left side. All these results were in the main confirmed by 
the section taken on the same day at high tide, as also by subsequent sections both 
here and at other sites ( vide Table I., 9th, 16th, 23rd, and 30th January and 6th 
February; also Table II.; also Table III., especially 1 6th, 23rd, and 30th January 
and 6th February). It was to be anticipated, however, that the local currents would 
not be constant, and subsequent observations showed them to be always changing 
their position. But the point of practical importance was that they did not in any 
marked manner affect the distribution of salt at the surface. 
Influence of Tides.— It was expected that the saltness of the water would vary 
with the tide, and it seemed not improbable that, in case the river might be excessively 
salt with one tide, sufficiently fresh water might be obtained by pumping only during 
