To the northward of Treaty point, and N. N. W. from Cape Kami-Saki, distant fourteen miles, is Yokuhama bay. To reach this anchorage, bring the wooded bluff which terminates the high land on the north side of the bay to bear N. by W. ½ W., and steer for it until Treaty point bears S. W. by S.—(this clears the spit off the point); then haul up about N. W. by N. for the bluff over the town of Kanagawa, and anchor in five and a half or six fathoms, with the Haycock just open to the eastward of Mandarin bluff. Mandarin is the steep bluff a mile to the northward of Treaty point.
A flat extends out from the northern shore of this bay, between Kanagawa and Beacon point from one to two miles; off Mandarin bluff there is also a shoal extending a mile to the northward.
The bay of Yedo is about twelve miles wide, and thirty deep, with excellent holding-ground, and capable of sheltering the fleets of the world.
Our survey embraced the western shore only, from Cape Kami-Saki to Beacon point. We had no opportunity of examining the eastern side. The soundings from Treaty point across in an E. S. E. direction are regular, and three fathoms were found about a mile and a half from the opposite shore.
Of Uraga channel, a reconnoissance was made of the western shore only.
During our stay in the bay, from the 17th February to the 18th April, the weather was generally fine, being occasionally interrupted by strong winds and heavy rain. The gales came up suddenly from the southward and westward with a low barometer, and continued for a short time, when the wind hauled round to the northward and westward, and moderated. We had no easterly blows; in fact, the wind was rarely from this quarter, except when hauling round from the northward (as it invariably did) by east to the southward and westward.
The tide is quite strong out in the bay; and off the tail of Saratoga spit, Perry island, and Cape Kami-Saki, its velocity is much increased. But at the anchorage in the bay of Yokuhama it was scarcely felt. At Yokuhama the Japanese, authorities supplied us with wood and water, and a few vegetables, fowls, eggs, oysters, and clams.
| Latitude, | Cape Sagami | 35° 06′ 30″ |
| Longitude, | ” | 139° 40′ |
| Latitude, | Webster Island | 35° 18′ 30″ |
| Longitude, | ” | 139° 40′ 34″ |
| Latitude | of Treaty building, north end of Yokuhama | 35° 26′ 44″ |
| Longitude, | ” | 139° 40′ 23″ |
| Variation | 25′ westerly. | |
| High Water, F. and C | 6 hours. | |
| Rise and fall at Yokuhama | 6 feet. |