I shall now quit this country with a few observations relative to the currents and tides upon the coast. From latitude 32 deg., and somewhat higher, down to Sandy Cape, in latitude 24 deg. 46’, we constantly found a current setting to the southward, at the rate of about ten or fifteen miles a-day, being more or less, according to our distance from the land, for it always ran with more force in-shore than in the offing; but I could never satisfy myself whether the flood-tide came from the southward, the eastward, or the northward; I inclined to the opinion that it came from the southeast; but the first time we anchored off the coast, which was in latitude 24 deg. 30’, about ten leagues to the south-east of Bustard Bay, I found it came from the north-west; on the contrary, thirty leagues farther to the north-west, on the south side of Keppel Bay, I found that it came from the east, and at the northern part of that bay it came from the northward, but with a much slower motion than it had come from the east: On the east side of the Bay of Inlets, it set strongly to the westward, as far as the opening of Broad Sound; but on the north side of that sound it came with a very slow motion from the north-west; and when we lay at anchor before Repulse Bay, it came from the northward: To account for its course in all this variety of directions, we need only admit that the flood-tide comes from the east or south-east. It is well known, that where there are deep inlets, and large creeks into low lands running up from the sea, and not occasioned by rivers of fresh water, there will always be a great indraught of the flood-tide, the direction of which will be determined by the position or direction of the coast which forms the entrance of such inlet, whatever be its course at sea; and where the tides are weak, which upon this coast is generally the case, a large inlet will, if I may be allowed the expression, attract the flood-tide for many leagues.
A view of the chart will at once illustrate this position. To the northward of Whitsunday’s Passage there is no large inlet, consequently the flood sets to the northward, or northwestward, according to the direction of the coast, and the ebb to the south, or south-eastward, at least such is their course at a little distance from the land, for very near it they will be influenced by small inlets. I also observed that we had only one high tide in twenty-four hours, which happened in the night. The difference between the perpendicular rise of the water in the day and the night, when there is a spring-tide, is no less than three feet, which, where the tides are so inconsiderable as they are here, is a great proportion of the whole difference between high and low water. This irregularity of the tides, which is worthy of notice, we did not discover till we were ran ashore, and perhaps farther to the northward it is still greater. After we got within the reef the second time, we found the tides more considerable than we had ever done before, except in the Bay of Inlets, and possibly this may be owing to the water being more confined between the shoals; here also the flood sets to the north-west, and continues in the same direction to the extremity of New Wales, from whence its direction is west and south-west into the Indian sea.