5 HYDROGRAPHIC REPORT. 
‘On the eastern coast, twenty-five miles from the head of the Gulf, is a small bay. The harbor 
of Guaymas is entirely land-locked, and is secure and spacious. The depth of water is from 
four to six fathoms, permitting the ingress of ships of the heaviest draught. 
Upon some of the islands in the Gulf there is guano, and several are known to contain valuable 
metals. Upon Carmen island are valuable deposits of salt. The waters of the Gulf abound 4 in 
whales, seals, turtles, &c. 
Below the harbor of San Felipe is a low black cape, and at this place the lofty and barren 
mountains, which border the shore as far as Cape St. Lucas, leave the coast and trend towards 
the northwest. Ten or fifteen miles northeast of Black cape, and a little east of south from the 
mouth of the river, is a rock one or two hundred feet high, white with guano, the sides rising 
abruptly from the water. Approaching from the south it bears a strong resemblance to a vessel 
sailing before the wind. A reef runs from the base in a northwest direction for at least one or 
two miles, and not being laid down upon the charts might hazard the safety of any craft passing 
near at night. Abreast of Ship Rock I found between seventeen and eighteen fathoms. 
Lieutenant Derby states that in 1850 he found the depth in the same locality twenty fathoms. 
The bottom being remarkably flat and uniform, it would appear from this that the Gulf towards 
its head is rapidly filling up. 
Beyond the rock the shores on both sides come in sight, and the Gulf narrows till it is only 
four or five miles in breadth. The water gradually shoals to two and a half or three fathoms, 
and becomes red and turbid. The bottom is a soft ooze, feeling like grease to the fingers. 
Two islands, Montague and Goree islands, and a bar twelve or fifteen miles wide, obstruct the 
mouth of the river. In the channels across the bar there are only ten feet of water. In the 
channel of the river, above the bar, as Rr 8 as the head of tide water, the depth varies from 
twelve or fifteen to thirty-five feet. ; 
The country on both sides is a flat expanse, entirely overflowed by the spring tides, which 
render it, during much of the time, a sheet of soft mud. The lines of the shore and the channels 
upon and beyond the bar are shifting and changeable, and shoals and islands are in constant 
progress of formation and removal. For twenty miles above the mouth the navigation is rendered 
— dangerous by the strength and magnitude of the spring tides. These have a rise 
and fall of from twenty-five to thirty feet, and a flow of extraordinary velocity, varying from 
five to seven or eight milesanhour. The flood is preceded by a ‘‘bore’’ or huge tide wave, from 
four toseven feet high. In the bends around Point Invincible and Howard’s Point it is very power- 
ful and violent, but loses its force as it ascends, and at a distance of thirty miles is scarcely felt. 
There are curves of the shore, as at Robinson’s Landing, where the rush of water is broken, 
and vessels may lie at anchor in comparative safety. Upon the shoals are formed what are 
ealled ‘tide rips,’’ where the sudden check to the surging mass causes it to bound along in 
high successive waves. The neap tides have a rise and fall of only ten feet, and a velocity of 
two and a half or three miles an hour. 
No opportunity has ever been afforded of making continuous observations upon these tides. 
At some seasons of the year the full moon, and at others the new moon tides are greatest and 
most violent. Similar alternations take place in regard to the day and night tides. There is 
no slack water. The ebb running out encounters the flood and is turned back, the current 
instantly setting in the opposite direction. 
The draught of vessels plying to the mouth of the river should not exceed eight or ten feet. 
If they carry freight that is to be discharged upon the decks of the river boats, they usually 
anchor near the west bank, in the vicinity of Robinson’s Landing. The best approach across 
the bar can be determined by experiment only. On several occasions vessels have crossed 
along the western shore. Lieutenant Derby followed the California coast. At the time I 
passed the deepest channel appeared to be between Montague and Goree islands. The most 
sheltered spot should always be selected for an anchorage, and where there is sufficient depth 
