530 APPENDIX. 



Your route or courses must be kept by compass : this you will find 

 no difficulty in doing in an open country ; but through the woods it 

 will be better that all your party should be required to keep their own 

 reckoning, which you will use, together with your own, in the same 

 way as at sea. The longitude of Fort Nisqually for your departure 

 you may take as 122° 53' W., its latitude 47° 07' 30" N. To serve 

 you for more accurate measurement than mere guess, time the paces 

 of your horses, and the length of each pace will be your scale. 



You will map or keep a diagram of your work on the pages of your 

 journal, taking the ruled lines as a convenient scale of miles, marking 

 thereon the mountains, hills, woods, rivers, brooks, and plains, within 

 your horizon. This will be more effectually done by ascending any 

 hill to take a bearing from. Every remarkable object you will desig- 

 nate by its native name ; if it has none, give it one of your own. 



A tape-line is furnished you to get any measurements with, such as 

 the width of rivers, &c. ; also find the velocity by the distance a chip 

 will pass in a given time. You will measure also any remarkable 

 trees you may meet with, their height and circumference. At all 

 your stopping-places you will take a reading of the barometer, and the 

 thermometers will be read every six hours, and as often besides as 

 your change of altitude may make it desirable. As it is one great 

 object to ascertain the height of all ranges, you will be particular in 

 noting the barometer on them, and it will be desirable for some one 

 of the party to ascend all remarkable hills : the barometer will also be 

 sent ; it is hoped that great care will be taken that it is not injured. 



It may be desirable for Dr. Pickering and Mr. Brackenridge to 

 make occasional short excursions from your direct route ; you will in 

 that case afford them all the facilities in your power to promote their 

 researches. 



You will study the safety as well as the comfort of your party, and 

 bear in mind particularly the instructions for the treatment of the 

 natives in my General Order of May 1st, 1841. 



Finally, you are not to deviate from the route pointed out unless 

 insurmountable difficulties should render it impossible to pursue the 

 course specified, and in no case are you to go to the southward of the 

 limits pointed out. 



Wishing you success in the execution of these instructions, 



I am, &c, 



Charles Wilkes, 

 Commanding Exploring Expedition. 



Lieutenant R. E. Johnson, 



U. S. Brig Porpoise. 



