The ebb and flow of the ocean is very slight in islands remote from any continent, as for example, at St. Helena, where it seldom exceeds three feet. Tides are remarkably high on the coasts of Malay, in the Straits of Sunda, on the open coast of Patagonia, along the coasts of China and Japan, at Panama, in the Gulph of Bengal, and at the mouth of the Indus, where the water rises thirty feet in height. Tides are greatest in any given line of coast, in narrow bays and estuaries; and are least in the intervening tracts where the land is prominent. {16c} On the authority of the late Captain Hewett, R.N., at the entrance of the estuary of the Thames, the rise of the spring tides is eighteen feet; but when we follow our eastern coast from thence northward; towards Lowestoft and Yarmouth, we find a gradual diminution, until at the place last mentioned the highest rise is only seven or eight feet. From this point there begins again to be an increase, so that at Cromer, where the coast again retires towards the west, the rise is sixteen feet; and towards the extremity of the gulph called “the Wash,” as at Lynn and in Boston Deeps, it is from twenty-two to twenty-four, and in some extraordinary cases, twenty-six feet. From thence again there is a decrease towards the north; the elevation at the Spurn Point being from nineteen to twenty feet, and at Flamborough Head, on the Yorkshire coast, from fourteen to sixteen feet. It is also recorded, on the authority of Captain Beaufort, R.N., that at Milford Haven, in Pembrokeshire, at the mouth of the Bristol Channel, the tides rise thirty-six feet, and at King-road, near Bristol, forty-two feet. At Chepstow, on the Wye, a small river which opens into the estuary of the Severn, they reach fifty feet, sometimes sixty-nine, and even seventy-two feet. {17} The tides at Tonquin are the most remarkable in the world. In this part there is but one tide and one ebb every twenty-four hours; whereas in other places there are two. Besides twice in each month there is no tide at all, when the moon is near the equinoctial, the water being for some time quite stagnant. These, with other peculiar appearances attending the same phenomena, were considered by many as inscrutable; but Sir Isaac Newton adjudged them to arise from the concurrence of two tides, one from the South Sea, and the other from the Indian Ocean. Of each of these tides there come successively two every day; two at one time greater, and two at another that are less. The time between the arrival of the two greater is considered by him as high tide; the time between the two lesser as ebb. In short, with this clue that great mathematician solved every appearance, and so established his theory as to silence every opposer. This fluctuation of the sea from the tides, observes the same author, produces another and more constant rotation of its waters from the east to the west, in this respect following the course of the moon.