580 JOURNAL OF SCIENCE. 
struck heavily on the bar when trying to enter about 30 years ago, 
and it was not until her second attempt that she succeeded in 
coming inside. 
If we go further) back and consult geological indications, there 
are strong evidences that at one time the present harbour of 
Otago was a strait, with the present north-west side as [the main- 
land, and the Peninsula as a detached island. The tides must 
then either have met and shed somewhere in the straits, or there 
were two distinct branches, one through between the mainland and 
the island, and the other quite to seaward of the island. The 
present St. Kilda and South Dunedin flats, and also the spits and 
bar at the northern heads would then originate and develop by the 
action of the currents and eddies at the meeting points of the 
straits and the main ocean, and the greater exposure of the 
southern extremity, and also the debris brought down by the Water 
of Leith, would cause that entrance to become completely blocked 
betore the northern one. The boring and dredging operations in 
the neighbourhood of Dunedin show a formation alternating 
between the products of land-floods and sea-borne sand, while the 
spits and bar at the northern heads are pure sand down toa 
depth of 44 feet at least below low water. At the northern heads 
there is a distance of 96 chains between the volcanic cliffs, which 
at one time were the boundaries of the stream going and coming. 
Of this, 24 chains are covered by the present stream at high water, 
the remainder being low flat, either destitute of vegetation, or only 
having the usual marshy growth of rushes and coarse grass. This 
flat probably had its beginnings by that part of the stream being 
sooner retarded by the oceanic action than the other portion under 
shelter of Taiaroa Head, and hence the deposit of the solid matter 
borne by it. Further,—the current coming from the north would 
cling with its greatest force to the curved outline on the side of 
Taiaroa Head and Harrington Point, thus again leaving the north- 
western portion of current the more sluggish and the more likely 
to induce deposit. The present outer bar probably had its origin 
in the division of the currents by the sharp features of Taiaroa 
Head and a consequent zone of slackened speed between the two 
streams where solid matter in the water would readily settle 
down. 
The first accurate record of the depths of water in the Har- 
bour is that furnished upon survey by Captain Stokes in 1849, 
Since then, in 1875 and 1879, the Upper and Lower Harbours 
were surveyed by Mr. D. L. Simpson for the Otago Harbour 
Board ; and more recently, in 1882 and 1883, special surveys of 
the bar and its neighbourhood have been made by the Public 
Works Department for the Government, and under the direction 
of the author for the Harbour Board. A comparison of the 1849 
and 1879 surveys along the line of the deepest water between the 
islands and the heads shows marked improvement in the latter 
one, both as regards the regularity of the bottom and the depths 
of water. In the earlier survey the least depths were 20 feet near 
Acheron Point, and 15 feet near the Maori Jetty; now there are 
23} and 27% feet respectively. The latter spot was for long known 
as the ‘‘ inner bar,” and was a serious inconvenience to the navi- 
gation of that part. A bank lying between this and the Peninsula 
began to disappear in 1864, and changes in the form of the bottom 
