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In certain narrow bends it is verv powerful and violent, but gradually 

 loses its force as it ascends, and at a distance of thirty miles is scarcely 

 perceptible. Along wider portions of the river there are curves of 

 the shore in which its force is not felt, and here boats may be safely 

 moored till this dangerous wave has rolled by. Upon the shoals are 

 formed what are called "tide rips," where the sudden check given 

 to the rushing volume of water causes it to bound along in high suc- 

 cessive waves. Steamboats that come to the mouth of the river 

 during the spring tides must descend from above tide water during 

 the ebb, and start to return two or three hours after the commence- 

 ment of the flood. 



The neap tides have a rise and fall of only ten feet, and a moderate 

 velocity. 



Between tide water and Fort Yuma the principal obstructions to 

 navigation are the sand bars. These become more frequent and 

 difficult as the river is ascended. The channel is exceedingly circuitous 

 and constantly changing. The average depth is about eight feet. 

 Shoals were frequently encountered, however, where there were 

 scarcely two feet of water. Experience alone can afford the capability 

 of navigating this portion of the river successfully. A knowledge of 

 the locality of the channel cannot be imparted, as it has been known 

 to shift from one bank to the opposite one in a single night. From 

 the formation of the banks, from the appearance of the water, of the 

 eddies, of pieces of drift wood and other floating substances, and of 

 the islands and bars visible above the surface, a practiced eye can do 

 much towards selecting the proper course, though boats rarely make 

 a trip between tide water and Fort Yuma, at the low stage of the 

 river, without grounding many times a day. The bars, however, are 

 composed of soft and loose material, and may always be passed with 

 more or less labor, depending in a great measure upon the skill shown 

 in the employment of the different methods of extrication resorted to. 



Below Fort Yuma there are no rocks. The snags are numerous, 

 but seldom dangerous. 



During the months of April, May, and June, while the river is 

 rising, and before new bars have had time to form, the navigation is 

 most easy. The average velocity of the current at low water is two 

 and a half miles an hour, during the July freshet from five to six. 

 The river at this season is about ten feet higher than during the 

 winter months. 



For three or four years an enterprising company has been engaged 

 in transporting government stores in steamboats from the mouth ot 

 the Colorado to Fort Yimia, and their persevering energy has so far 

 succeeded in overcoming the natural difficulties of the navigation as 

 to enable them now to perform the trips with entire regularity and 

 certainty. 



For one hundred and eighty miles above Fort Yuma the navigation 

 has a character similar to that already described. The river passes 

 through several chains of hills and mountains, forming gorges of 

 canons, sometimes of a considerable size, and in tliese there is gen- 

 erallv a better cliannol than in the valleys. 

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