Deedes Soe os» ie ea 
HYDROGRAPHIC REPORT. 13 
the last a line should be taken ahead to prevent the possibility of the boat swinging against 
some rocks that project near the channel. 
The rapids between Camps 54 and 55 are neither shoal nor very swift; but abreast of the 
latter camp is a long rapid, where there are only two feet of water. No others are now encountered 
till the Black cafion is reached. At the mouth of the cafion there is a short deep rapid, above 
which, in the centre of the channel, is a sharp conical rock, the top of which is about four inches 
below the surface. 
During the season when the river is high the current in this part of it would be swifter than 
below, but excepting for this, the navigation of this section of the Colorado would present little 
difficulty or hazard after the position of the sunken rocks should become known. A boat draw- 
ing not more than eighteen or twenty inches could at all times ascend and descend, without 
being lightened of its cargo, and perhaps experience less trouble from the rapids than 
from the sand bars in the lower part of the river. 
BLACK CANON. 
The black cajfion is twenty-five miles long. It contains twenty-five or thirty rapids. The 
presence of large rocks in the centre and along the edges of the channel renders many of these 
_ rapids dangerous. At two or three, and at Roaring rapid in particular, the fall is considerable, 
and the rush of water violent. Over any one of them, however, a steamboat of proper con- 
struction, partially or entirely lightened of the cargo, could be taken with the assistance of 
lines, but the passage of the cafion, at low water, would be tedious, and attended with much 
labor, hazard, and expense. 
In some of the narrowest portions of this gigantic defile, drift-wood was seen lodged in cre- 
vices fifty feet above the surface of the river, an evidence of the astonishing height to which 
the water has banked up during the summer freshets. The attempt to go through the cafion 
at any season when a sudden rise might be apprehended would be accompanied with grave peril. 
At the beginning of the warm weather, when the water has risen only one or two feet, the cafion 
might be navigated without serious trouble or danger; but the uncertainty and risk attending 
the passage, for the greater portion of the year, are such that the mouth of the cafion should be 
considered, for all practical purposes, the head of navigation of the Colorado. 
Above the Black cafion the river soon becomes a continuous rapid, utterly impracticable to 
be ascended in boats. 
DESCRIPTION OF BOAT TO BE USED UPON THE COLORADO. 
With a boat of proper construction the Colorado can be navigated without trouble, at all 
seasons of the year, between the head of the Gulf of California, and the mouth of the Black 
cafion. The most essential conditions in regard to the boat are as follows: 
Ist. That she should not draw more than twelve inches when light. 
2d. That the boiler should be of large capacity and the engines of great power. 
3d. That she should have a large stern-wheel. 
4th. That the bottom should be perfectly flat and smooth. 
5th. That the hull should be divided by water-tight bulkheads. 
For service upon the river I would recommend iron boats in preference to wooden ones. In- 
the hot climate of New Mexico the former would be more durable; they can be built of lighter 
draught for the same capacity; are cheaper, and more easily and rapidly put together. A 
good description of boat would be an iron stern-wheel steamer, with the hull one hundred 
feet long, and the greatest breadth of beam twenty-two feet; built sufficiently full to insure. a 
draught, when light, not exceeding twelve inches; if in sections, the flanges, where the sections 
meet, to be turned inwards, in order that the bottom may be perfectly smooth and flat; to have 
a large boiler and a powerful high-pressure engine, with two fourteen-inch cylinders of five 
