SURVEYS. 



Porpoise and Oregon, being in company : they were brought into the 

 triangulation, and were employed in carrying on an independent set 

 of observations, through azimuthal bearings and distances by sound, 

 when at their several anchorages, which went to prove the other ope- 

 rations. A series of stations were also occupied on the land, where 

 the latitudes and meridian distances were determined by observation. 

 The close agreement of all the results proved that the survey was 

 entitled to great confidence. 



The " sounding out" formed a distinct part of the work, and was 

 made on the return down the river. Each officer engaged thereon was 

 furnished with a diagram of the section of the river he was ordered 

 to sound out, taken from the original plotted chart, and on it the lines 

 to be " sounded out" were drawn to the signal-points, as well as to in- 

 termediate points between the signals : these latter were fixed by the 

 three-point problem, or by measured distances from signal-points. 



During the absence of the river party, the sounding out of the Bar 

 at the mouth of the Columbia was effected, and the soundings placed 

 upon the projection, which had been previously made and furnished 

 the officer in charge of the Flying-Fish and two boats. After this 

 manner the whole extent of the Columbia, from the sea to the highest 

 point of navigation, together with its branches, was surveyed. The 

 survey began on the 12th of August, and was finished on the 10th of 

 October. 



For the purpose of showing the triangulation, both primary and 

 secondary, I have selected a part of the Columbia River, a diagram of 

 which will be found on Plate 1, Fig. 2. As the character of the lines 

 on it is given, it is not deemed necessary to offer any further remarks 

 in explanation. 



After this view of the surveying operations, I think it will be ad- 

 mitted that our duty was energetically performed, and that a greater 

 amount of work could not have been executed in a shorter time, even 

 under the most favorable circumstances. 



The surveying and hydrographical duties, although so extensive, 

 have been fully proved by navigators who have followed us. It would, 

 however, be surprising if there were no errors : yet I am satisfied there 

 are but few; and from the reports of those who have had an opportu- 

 nity of using the charts, I am confident that nothing essential to navi- 

 gation and the interests of commerce has been neglected or overlooked 

 in them. 



