Full tide in the estuary of the Tay is generally said to occur, on the days of the new and full moon, at a quarter past two o'clock, but in the harbour of Dundee it flows till about half-past two. The average height of the spring-tides, as measured by an index at the entrance to King William's Dock, is about seventeen feet, while that of the neap-tides is about eleven feet. The water opposite the town, though saline, is not wholly marine, but considerably diluted by the fresh water flowing down the river; and this is the reason, probably, why sea-water insects never attack the piles, buoys, or beacons about the harbour. Opposite the town, the river Tay is very nearly two miles broad. The channel across is much interrupted by a sand-bank, which, though formed within the last forty years, has now at full spring-tides only about ten feet water over its surface, and at neap-tides scarcely more than four. Its position is not far from midway across; its form is spindle-shaped; its length, as seen at low water, upwards of a mile; and its course parallel with that of the river. At present, its lower or eastern extremity is stretching down in the form of a curve, concave towards the harbour of Dundee; but it is so constantly altering its features, that no further remark need be made upon it than this, that it is always accumulating, and slowly moving down the river. This sand-bank, in reference to the navigation of the Tay, is naturally an object of no small interest and solicitude. [Illustration: ABBEY OF ARBROATH.] THE ABBEY OF ARBROATH. The Harbour, which was originally at the end of the East Causeway, was formed about the remote period of 1194; but being ill-constructed for the craft and increasing traffic of more modern times, a brief or bill was obtained for building a new pier in 1725, and which is situated a little to the westward of the old one. It is strongly built of stone, and, though not capacious, is sufficiently commodious to admit of vessels lying close to any part of it, either to receive or discharge their cargoes. During spring-tides there is a depth of from fifteen to sixteen feet of water at the entrance, and at neap-tides of from nine to ten feet; but it is dry at low water. Here, as in most of the other ports of this coast, there is a considerable foreign trade carried on with Russia, Norway, and Sweden, as well as a home-trade in lime, coals, and agricultural produce. The trade at this port is now so rapidly increasing, that great improvements in the harbour are contemplated. It counts seventy-seven vessels of its own, registering 6700 tons.