quite a quarter of a mile; the depth varying from twelve to thirty feet, and the total dimensions of the channel cannot be less than this at any point: lower down, but must, in fact, be greater, since the velocity of the current is less; if, therefore, the depth of the channel be less, it must arise from unfavourable circumstances leading to its divergence in width.

The circumstances under which the egress of the Harbour meets the sea are, in many respects, favourable. Thus, it debouches into Foveaux Straits, which are effectively protected from the great swell of the Southern Ocean by Stewart’s Island. The advantage which the Harbour enjoys in this respect over those on the west coast of the North Island is immense, and is clearly marked by the fact that the sea rarely breaks all across the channel of the New River, in which there is sixteen feet of water, while it frequently breaks all across the channels of the Kaipara and Manukau, in which there are upwards of thirty feet of water.

But the unfavourable circumstances of the mouth of the New River are these: the southern shore, which consists of a pretty straight rocky beach, of which Omaui Island may be considered the outer extremity, greatly overlaps the North Head, which lies to the north-east of Omaui Island, at a distance of two or three miles. Now, the best course for the channel, and that which the ebb-tide would naturally take, lies along the southern shore; and a channel there, with the full force of both ebb and flood tides flowing through it, would always be deep, because confined by the rocky shore; but the flood tide, coming in from the westward, strikes all along the straight line of the bar, and in its present position sweeps over it, and the prevailing winds being in the same direction, the “water of translation” roll conventionally varying angles over its long outer edge, smoothing every inequality and causing the tide to spread itself evenly over the whole breadth, and consequently to a very shallow depth. A portion of the ebb follows the course so laid open to it, and thus the scour of by far the greater part of the tidal current is wasted without any useful effect on the Harbour channel, with the further disadvantage of cross action of the tides, the flood running, until quite recently, at right angles, to the course of the ebb.

While, however, the tendency of the flood-tide is to force its way in from the south-west and so to keep open a broad shallow channel all along that line, there is another and an opposite influence at work, which, when favourably directed, may effectively control the former one; and which, I think, has done so incomparably recent times. There can be no doubt that here, as under similar circumstances elsewhere, great quantities of sand travel continually from west to east. Now, transported by the harbour tides, this would be deposited on the northern part of what is now the bar, and would form a great mangular spit running out from the North Head, and the Harbour would then be in its best condition.

I think that the form of channels shown on the earliest map, and all the changes which are known to have taken place afford a strong presumption that this was once the case, and that a breach was subsequently made through this spit near its southern extremity, probably in a season of great floods following a very fine one, when the channel had become contracted by a diminished flow of water. As soon as this breach was made, the tides, especially the flood, would be divided into two branches: at an obtuse angle inside the bar. Along the line of contact of these two currents a space of slack water would be formed, and any sand brought to that point by the force of the current would fall. This appears clearly to be the origin of the spit, as I find it on Mr. Thomson’s chart.

It is obvious that such a spit, especially at the commencement, when it was still small, would be subject to great and sudden changes as the circumstances of strong westerly winds or of great river floods gave preponderance to either rolling in of the flood-tide through the breach in the bar, or to the efflux of the ebb by the inshore channel. This quite agrees with the earliest accounts we hear of the Harbour, when it is stated that for a short time the inshore channel was almost closed near the Pilot Station.

It is quite clear that for the past seven years at least, this outer channel has continually increased in width, and so has more and more left in the flood-tide and also the action of the waves, which last mainly contribute the great wearing of the North Spit, by which a broad and deep channel has been excavated, whereas few years ago the sand was dry at three-fourths ebb. A short break in the spit near the south-west end, with the westerly winds and a moderate sea, would send along the edge of the channel, and this ebb