76 NORTHWESTERN BOUNDARY OF UNITED STATES. [bull. 174. 
The reconnaissance work extends over an area of about 30,000 
square miles. Within this space the barometrical heights of over 800 
points have been obtained. 
A magnetic survey, extending over a range of 3° 20' in latitude and 
4° in longitude, with the necessary observations of the magnetic ele- 
ments of the astronomical stations, was also made. 
The entire length of the land boundary line is over 9° in longitude, 
or about 410 miles, and the length of the route traveled in surveying 
it is double that distance. Trails had to be opened for three-fourths 
of the distance traveled, involving great labor in cutting, grading, 
and bridging to make the route practicable for pack-mule transpor- 
tation. The water-courses were numerous and rapid, rendering the 
fords frequent and dangerous; and a slight rise of many of the streams 
would have made them impassable but for the timely precaution of 
building bridges at small streams and ferry boats at the river cross- 
ings. Many of the trails opened are now traveled routes to the 
mines then and since discovered, which are rapidly developing that 
section of the country, where almost every valley of any extent affords 
facilities for agricultural pursuits. 
In collating the results of the survey reports upon the geology, 
botany, and natural history of the country reconnoitered were pre 
pared, and complete maps, on a large scale, made of the entire boundary 
and the adjacent country. A general map has also been made, show- 
ing the extent of the country traversed. And to facilitate the survej 
of the public lands, photographic duplicates of the detailed sheets, 
showing each monument on the boundary line, with its geographical 
position, were furnished to the General Land Office. Photographic 
duplicates of the detailed sheets of the water boundary have also been 
made and furnished the Department of State in illustration of the 
question of the boundary channel. 
I have the honor to be, very respectfully, your obedient servant, 
Archibald Campbell, 
Commissioner Northwest Boundary Survey. 
Hon. William H. Seward, 
Secretary of State. 
