THE COLORADO RIVER

165 shore 12 to 6 miles. Parts of this coast are subject to overflow at times during heavy freshets and at highest spring tides.

Ometepes Bay, situated about 27 miles northward of Point San Felipe, has an entrance about 100 yards wide and 1/4 mile in length, with a depth of 3 fathoms at half tide. The bay, circular in form, is about 3 miles in diameter and has general depths of 5 fathoms. It is landlocked and free of hidden dangers. The rise and fall of the tide is said to be about 25 feet.

THE COLORADO RIVER has its source in the Rocky Mountains, being formed in Utah by the Union of the Green and the Grand Rivers, the former rising in Wyoming and the latter in Colorado, and empties into the head of the Gulf of California. Together with the Green River, which may be considered the upper continuation of the Colorado, it has a course of about 1,700 miles, and, with its tributaries, drains an area about 800 miles long by 300 to 500 miles wide. At Yuma, Arizona, about 75 miles above Philip's Point, it is joined by the Gila River from the eastward. Between Troma Point, about 8 miles below Yuma, and a position 20 miles below that point the river forms the boundary between the United States and Mexico. The entrance to the Colorado River may be considered as lying between Shoal Point, on the Sonora shore, and Sargent Point, 27 miles westward of it, on the coast of Lower California; it is much obstructed by mud flats, which are bare at low water springs, but are separated by navigable channels at high water. Montague and Gore Islands, lying in the mouth of the river, are subject to overflow at high water springs. The main channel lies close along the eastern side of these islands.

Shoal Point (31°33′ N., 114°19′ W., H. O. Chart 800) is a low, sandy point, with a barren sand hill about 300 feet high immediately behind it. A shore bank extends about 1/2 mile off the point, and a shoal with a least depth of 21⁄2 fathoms lies 2 to 4 miles northwestward of it. Between this shoal and the shore there is a channel over 1/4 mile wide, with depths of 5 to 7 fathoms.

The coast southeastward of Shoal Point is described in the next chapter, page 169.

Tides.—The high water interval at full and change at Shoal Point is about 0h. 30m.; springs rise 25 to 30 feet, neaps 6 to 10 feet.

Direction Sandhill.-At about 9 miles northwestward of Shoal Point the beach projects slightly, and behind it are some sand cliffs at the foot of the hills which form the lateral spurs of a long, barren tableland. Direction Sandhill, which lies behind this projecting beach, is 556 feet high and is easily distinguishable from the neighboring hills by a growth of bushes at its foot. It is an excellent mark for entering the river. (See view B on H. O. Chart 800.)

Shoal.-Off the point just mentioned there is a shoal with a least depth of only 9 feet; between it and the shore there is a channel 34 mile wide, through which 6 fathoms may be carried at low water. There is also a channel about 1 mile wide, with depths of 5 to 6 fathoms in it, westward of this shoal, between it and an extensive mud flat which uncovers at low water springs.

Santa Clara River, which empties into the gulf at a point about 10 miles from the low point that fronts Direction Sandhill, is navigable only at high water; at low water springs it falls dry, leaving only a few pools of water along its course.

The sand hills and tablelands, which up to this position have run parallel to the coast, here assume a more northerly direction, following the course of the Santa Clara River.

Beacons.-Santa Clara Beacon, on the western side of the mouth of the river, consists of two piles with a cross piece at the top.

White Beacon, consisting of piles with a triangular cage, stands on a shoal spit that extends off from the west side of the mouth of an extensive slough 5 miles west-northwestward of Santa Clara Beacon. A cross-shaped beacon stands on the opposite side of the slough, 400 yards north-northeastward of White Beacon. These two beacons serve as guides for entering the slough and for avoiding a shoal which extends a short distance off its mouth.

Port Isabel, now abandoned, is situated on the east bank of the slough about 24 miles from its mouth, at the first good landing place; the shores nearer the mouth consist of very soft mud.

Philip's Point lies 25 miles northwestward of Shoal Point and about 111⁄2 miles beyond White Beacon. Above it the channel soon becomes shallow and tortuous, and the navigation more difficult.

The north shore of the river, from the mouth of the Santa Clara to Philip's Point and for several miles beyond, is almost level alluvial plain, subject to overflow at high spring tides.

Philip's Point is generally marked by a beacon which, however, is not to be depended upon; the point is prominent but it becomes flooded over at spring tides and when the river is in flood. (See view A on H. O. Chart 800.)

Montague Island, lying on the south side of the main channel abreast Red Point, is a low, flat island with a length of about 6 miles and a maximum width of 3 miles. It is covered with coarse grass and scattered driftwood and logs; it is subject to overflow at the time of freshets and of spring tides.

The passage between the island and the west bank of the river may be used at high water by small vessels, but it dries at low water springs. A drying mud bank extends 9 miles southward of the island, along the Lower California shore.

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Gore Island (31°43′ N., 114°43′ W., H. O. Chart 800), 2 miles long, north and south, 3⁄4 mile wide, and similar in character to Montague Island, lies 3/4 mile eastward of the southern part of the latter. These islands are separated by a channel in which there is at all times a depth of more than 1 fathom, except on a narrow, drying bar, 400 yards wide, at the junction of this channel and the main channel, opposite Philip's Point. A drying mud bank, similar to that southward of Montague Island and separated from that bank by a channel, extends off to the southward and eastward from Gore Island.

Bomba (H. O. Chart 619), 21 miles above Philip's Point, is now at the head of navigation for the lower reaches of the Colorado River. There is steamship service from Bomba to Santa Rosalia and Guaymas, and transportation by automobile and truck to Mexicali.

Channel. The main channel, through which 21⁄2 fathoms may be carried at ordinary low water as far as Philip's Point, lies close along the Sonora shore. About 3 miles eastward of Gore Island, between the mud bank extending off from it and another similar mud bank, 13 miles in length, which lies on the southwest side of the main channel, is a channel nearly 1 mile wide, through which 14 fathoms may be carried; it joins the main channel nearly opposite the mouth of the slough.

The head of tide water reaches above Mayor, which is 33 miles, straight line distance, above Philip's Point.

Anchorage. The best anchorage is eastward of Philip's Point in a depth of about 32 fathoms (at low water springs), over mud bottom, about 400 yards off the mouth of a small creek midway between the point and White Beacon.

Tides.—The mean high water interval at Philip's Point is 2h. 15m.; the spring range is 31.5 feet, the mean range 21.6 feet.

Currents.-The tidal currents run with great strength at full and change of the moon, sometimes as much as 6 knots; there is no slack water. The influence of the tide is felt for about 40 miles up the river, a few miles above Heintzelman Point. At a short distance above Philip's Point the spring tide comes in as a bore, or bank of water, 4 feet high, extending in one huge breaker clear across the river, while the ebb is still running out.

The winds at the mouth of the river are mostly from the northward and in summer are very dry and hot.

Directions. To enter the Colorado River by the main channel: After passing Consag Rock steer so as to keep it astern, bearing 185°. When Direction Sandhill is made out about ahead, steer for it on a course of 4°. When about 1/2 mile from the shore, in a depth of 5 fathoms, Shoal Point bearing 123°, steer 300°, passing inside the

sandy shoal off the point, until Direction Sandhill bears 92°, the shore then being distant 1 mile. From here follow the shore line at about the same distance, using the lead continually. When Santa Clara Beacon is made out steer for it until within 1⁄2 mile of the beacon and about the same distance from the shore, and then resume course 300°. Continue on this course until Range Hill is just open northward of Philip's Point, bearing 283°, and then steer in on this line, which leads through the deepest part of the channel; Range Hill, situated 24 miles west-northwestward of Philip's Point, is 813 feet high and has conspicuous white cliffs.

When passing White Beacon, at the mouth of the slough, haul a little to the southward in order to avoid the bank that extends off from the shore.

Caution.-Inasmuch as the mud flats and shoals are subject to frequent changes and as the beacons can not be relied upon, the foregoing directions should be used with caution. A vessel should not trust to compass course, as the currents may sweep her a long way off the line. The lead must be kept going continually. A vessel should enter the river on the first of the flood, and, in leaving it, should start on the last of the ebb.

CHAPTER V

THE COAST OF MEXICO AND ADJACENT ISLANDS FROM THE MOUTH OF THE COLORADO RIVER TO CAPE CORRIENTES

Remarks.-The coast of Mexico from the mouth of the Colorado River to Cape Corrientes bordering partly on the Gulf of California and partly on the Pacific Ocean, is, for the most part, low and sandy, although in many places the mountains approach it closely. In the distant interior may be seen the summits of the Sierra Madre and of the high mountain ranges branching off from it. The Mexican states of Sonora, Sinaloa, and Jalisco front on this stretch of coast. The interior of this country is fertile, but the principal source of wealth are the numerous gold and silver mines.

The islands off the coast are generally barren and uninhabited. Tiburon Island in the upper part of the Gulf of California, is inhabited by the Seris Tribe of Indians.

There are many anchorages and several ports along this coast; among the ports are Guaymas, Yavaros, Topolobampo, Mazatlan, and San Blas.

The depth of water on the east side of the Gulf of California is, in general, much less than that on the west side.

Currents.-Information regarding currents along this coast is rather meager and somewhat contradictory. The currents probably depend almost entirely upon the winds.

The currents between Guaymas and Cape Corrientes are strong and irregular during the rainy season, between May and November. Northerly currents are frequently encountered in this season, but southerly currents normally predominate. Tide rips are often seen along the edges of the shoals that lie off the coast.

Coast.-Beyond Shoal Point, the eastern entrance point of the Colorado River, the coast, trending east-southeastward for a distance of 10 miles, is generally low, with here and there a sand hill of moderate height. Shoal water extends offshore to distances increasing from 11⁄2 mile near Shoal Point to 2 miles at a position 10 miles farther east-southeastward.

Adair Bay is a wide indentation that is entirely open to the southward and is so filled with dangerous shifting shoals as to be impracticable for even the smallest coasters. Its western limit lies 10 miles east-southeastward of Shoal Point; and Rocky Bluff, the east

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