582 JOURNAL OF SCIENCE 
ning of 1862 was 16} feet, so this shows that not only is the bar 
liable to considerable fluctuations, but also that there is still a 
force of sufficient power to pare down the bar to fully the depth 
that it was before any works were executed in the upper har- 
bour. 
The average depth along the crest of the bar, north of the 
line of the leading lights, was in 1849—15.2 feet, and in 1879 
—15} feet. The lines at different times, though not coincident, 
still show the same average depth. On the other hand the north 
channel has made up, and where in 1849 the least depth was 22 
to 23 feet, it is now 20} feet, and the average depth along the 
line of deepest water has been reduced from 29 to 263 feet. The 
plan of the bar shows a widening towards the northern end, 
and also a tendency to turn in towards the shore. 
A map with the line of greatest depths upon it, shows it to be 
decidedly tortuous, keeping, however, in its average direction 
pretty nearly the same line as that of the strongest ebb tide until 
it impinges upon the bar, and is then deflected shorewards to with- 
in 30 chains of the northern cliffs, after which it turns abruptly 
seawards. If therefore the north channel were looked to as the 
permanent entrance, two very material disadvantages would have 
to be faced, in so far as the limiting depth is only 201 feet, and 
that ina position hopeless for improvement ; and also owing to 
its direction a vessel would sometimes be broadside on to the 
waves, and sometimes would be heading direct on towards the 
beach. There is no part of the north channel north of the pro- 
posed training wall which has so great a depth as 26 feet at low 
water. Measuring on the line of the leading lights, the distance 
between the inner and outer 18 feet contour line is 400 feet, and 
between the 26 feet lines, 1300 feet. That is, that to get a depth 
of 26 feet at low water, material must be removed from the bar 
for a length of quarter a mile, and average depth of 4 feet, by 
some process either of lifting and transport, or by scour. 
Bores to the number of 36 on the bar and its immediate 
neighbourhood, and 8 in the spit opposite Harrington Point, were 
put down by my assistant, Mr. Mason, and these showed the for- 
mation of those parts to be pure sand. The greatest depth 
reached was 44 feet below low water in the first series, and 30 feet 
in the latter. These probings were effected by a strong jet of 
water being sent down through a 3-inch tube, thus clearing the 
sand away from the bottom of it and allowing the tube to be easily 
pressed down to the required depth. 
There can be no doubt that the forces which developed the 
Otago bar are still in existence, and therefore any force operating 
in its reduction must be continuous. To prevent its further growth 
the present reducing agencies must not be diminished; but to 
accomplish a radical improvement in depth, these must be — 
strengthened and better directed. The principal deepening in- 
fluence is the tidal water passing out and in the harbour, and 
therefore the quantity of this should not be lessened by reclama- 
tion, unless either the commercial gain thereby is very great, or 
the loss of water can be compensated by other means. The com- 
pensation may take the form either of facilities for the more rapid 
filling up of the harbour by the tide; or it may be secured by im- 
provements in the neighbourhood of the bar. At the head of the 
——— lle ee 
