516 APPENDIX. 



and untiring in their use. Much of the information desired will depend 

 upon their use, and will demand your exertions and diligence. 



Observations will be obtained daily, if possible, both for latitude and 

 longitude. 



The meridian altitude of the sun, by the artificial horizon, you will 

 observe daily if possible, also that of the north star ; this observation 

 you will find easy after a little practice, by bringing the two reflected 

 images to cover each other. It is necessary to get the error of your 

 watch in mean time by a star, east or west, to find the true time. 



This can be done immediately before or after the observation by 

 the north star, and be better than to depend upon the rate of your 

 chronometer, which may alter in riding, though it is not probable it 

 will much. It must be carried in the chronometer-fob of your waist- 

 coat, which some of you may have near the arm. The best mode of 

 observing a star in the artificial horizon, is to clamp your index and 

 wait its contact. Choose for time those that are east or west, and of 

 altitude about 30°. If you observe about the same hour every night, 

 you will find the computation more convenient. 



All your observations must be worked up as soon as possible after 

 they are taken. 



6th. Your route or travel must be kept by compass: this you will 

 find without difficulty in an open country, but through the woods it 

 will be better that each of your party be required to keep his reckon- 

 ing, by which you can correct your own. 



The longitude of Fort Vancouver is 122° 39' 34" W., and its lati- 

 tude is 45° 36' 53" N., from which you will take your departure. 



7th. To obtain the distance of remote objects, base-lines may be 

 measured on the plains. For this purpose the steppings of a horse 

 will give the best results, by first measuring his steps in one hundred 

 or five hundred feet, and at the ends observe the angles and bearings. 



8th. A tape-line is furnished you for getting the measurement of 

 trees, short bases, &c, and any remarkable object you may meet 

 with. Attend to the velocity of rivers by the distance that a chip 

 will pass in any given number of seconds by your watch, and the 

 ratio of a log-line may be adopted. 



9th. At all your encampments you will get readings of your baro- 

 meter, and the thermometer will be taken every six hours, and as often 

 also as any change of altitude or temperature may require. 



If by any accident your barometer should be broken on the heights, 

 try the temperature at which water boils. 



It is required of you to obtain the heights of all mountain ranges and 



