Vessels from the southward, bound to this bay, should pass up to the westward of the chain of islands lying off the gulf of Yedo, and are cautioned against mistaking the deep bight of Kawatsu bay for the entrance of Uraga channel, for on the northeast side of this bay there is a ledge of rocks several miles from the shore, bearing from Cape Sagami about W. N. W., distant ten miles, upon which one of the vessels of our squadron grounded. A stranger without a correct chart would naturally make this mistake, as the opening of the channel is not seen at a distance from this quarter, the shore appearing as an unbroken line.
The entrance to the channel bears from the centre of Oho-Sima N. E. by N., distant about twenty miles. Stand in upon this line, and the Saddle hill to the northward of Cape Sagami will be readily recognised, as well as the round black knob on the eastern side of the channel. On approaching Uraga, the Plymouth rocks will be plainly seen; give these a berth of half a mile to clear the Ingersoll Patch, a sunken rock with but one fathom on it, and which is the only known danger in the channel.
Between Plymouth rocks and Cape Kami-Saki, the ground is clear and the anchorage good, if care be taken to get pretty well in, so as to avoid the strong tides which sweep round the latter with great rapidity. A spit makes out a short distance to the southward of Kami-Saki; but to the northward of the cape, the shore is bold, and the water very deep.
On rounding Cape Kami-Saki, if bound for the city of Yedo, steer N. W. by N., until Perry island bears S. by W. ¾ W., so as to clear Saratoga spit, which extends well out from the eastern shore; then haul up, keeping Perry island upon this bearing until the beacon on the low point to the southward of Yedo bears W. N. W. This clears the shoal off the point, and here there is good anchorage in about ten fathoms water, in full view of the city of Yedo.
At this point our survey terminated; the boats, however, found a clear channel, with plenty of water for the largest vessels, several miles farther to the northward, and within a few miles of the city.
If bound to the American anchorage, from Cape Kami-Saki, steer N. W., and anchor in eight or ten fathoms water, with Perry island bearing S. S. E., and Webster island S. W. by S.
To the southward of Webster island there is also good anchorage in six and seven fathoms. Near this anchorage, there are two snug coves, very accessible, in which vessels may conveniently repair and refit.
Susquehanna bay, three miles W. N. W. from Cape Kami-Saki, is well sheltered, but it contains a number of reefs and rocks, and is therefore not recommended as an anchorage.
Mississippi bay is four miles north of the American anchorage; it is well sheltered from the prevailing winds. Upon anchoring it is necessary to give the shore a wide berth, to avoid a shoal which extends out from half to three quarters of a mile. The conspicuous headland, or long yellow bluff, on the north side of this bay, is called Treaty point; a shoal surrounds the point from two thirds of a mile to a mile distant.
Between the American anchorage and Treaty point, the soundings are irregular, shoaling suddenly from twelve to five fathoms on a bank of hard sand.