XXVIII EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



than usually falls to the lot of a deputy surveyor, and tbat they will 

 not utilize these points unless required so to do by law. 



In the first of the above cases, we may suppose a valley, surrounded 

 by high, rugged mountains, over which it would be very expensive to 

 run a line at all, and impossible to do it with any approach to accuracy. 

 Suppose that a mountain peak on the edge of this valley has been ac- 

 curately located and its latitude and longitude given. The latitude 

 and longitude of the point in this valley which should be the nearest 

 township corner to this peak can easily be deduced by calculation, 

 whence the distance and direction of this supposed township corner 

 from the peak can also be computed. All that remains to be done, then, 

 is to find the point in the valley at the requisite distance and direction 

 from the peak, and this point is the township corner, whence the survey may 

 be carried on in the usual manner. Take, as an example, the valley of 

 the Uucompahgre, in Western Colorado, a large, fertile valley, which will 

 soon require to De surveyed. The nearest surveys are now, I understand, 

 on the Gunnison, at the mouth of Cochetopa Creek. To carry a base 

 line thence to the Uncompahgre Valley will require the chaining of 

 about 50 miles over rugged mountain country. Instead of this, take 

 Mount Sneffles, a peak in the San Juan Mountains overlooking this 

 valley, as a starting point. The township corner which will come near- 

 est to this peak is, we will say, the 8th township, i. e., 48 miles west of 

 *the last one at the mouth of Cochetopa Creek, where the surveys now ex- 

 tend. Knowing the latitude and longitude of the latter point, that of the 

 supposed corner in the Uncompahgre Valley, being 48 miles farther west, 

 can easily be computed, and knowing this, its distance and direction 

 from Mount Sneffles can also easily be computed, and the line run from 

 the summit of Snefflea to the required point. 



In the second case, that of using these points as checks on the accu- 

 racy of the land surveys, I would recommend that the surveyors, when- 

 ever, in running lines, they pass near a located point, be obliged to con- 

 nect their lines with it by chaining. Then the astronomical position 

 of the corner, as determined by their work, and by connection with the 

 station of triangulation, should agree. If they do not, the most of the 

 error is in the laud surveys, and they should be corrected accordingly. 

 This will not only vastly increase the accuracy of the work, but will 

 prevent the manufacture of the notes in camp. 



Moreover, these geodetic stations, which are in all cases mountain 

 peaks whereon the station is marked by an indestructible stone cairn, 

 would furnish points of reference for all time, in case disputes should 

 ariwse concerning boundaries, «S:c. 



Monuments are built on all the stations in the primary triangulation, 

 and on those of the secondary triangulation, wherever material for their 

 construction is available. They are built of stone, simply piled up in 

 the form of a pyramid ; are of a minimum height of 5 feet, thence up to 

 ] 5 feet. 



