114 LIEUTENANT MICHLEr's REPORT 



point on the Colorado is 32° 29' 44".45 north, and the longitude of same 114° 48' 41". 53 west 

 of Greenwich. The computed azimuth of the line connecting this point with the intersection 

 of the 111th meridian and parallel 31° 20' north, forming part of the boundary between the 

 United States and Mexico, is at the initial point 71° 20' 43". 8 southeast^ and at the intersection 

 69° 19' 45". 94 northwest, and its length 23Y. 63565 English miles. The mean of eighty barome- 

 trical observations at this point is 29.871 inches, — .020 for non-periodic error = 29.851 ; the 

 non-periodic error was obtained by comparison with observations made at San Diego. The 

 height of this point above the level of the sea at San Diego is 156.3 feet ; its distance below the 

 junction by the mcanderings of the river is 27.9 miles, making the mean fall of the river be- 

 tween these two points 4.26 feet per mile. 



The magnetic variation of the initial point in March, 1855, was 12° 37' 30" east of north. 



As it was impossible to mark the exact initial point in the middle of the stream, Mr. Jimenez 

 and myself established the first monument 3,164.84 feet distant from it, in the direction of the 

 line, at its intersection with the meridian of the observatory. The azimuth of this monument is 

 71° 20' 25" southwest. Monument II, of cast iron, and pyramidal in form, is placed on the 

 edge of the sand plain, as this position is more permanent and free from the action of freshets in 

 the Colorado. I give its astronomical position : Latitude 32° 29' 01". 48 north, and longitude 



114° 46' 14". 43 west of Greenwich. 



71 



distance from the initial point is 4,522.9 yards. This monument erected, everything was in 

 readiness to prolong the line. An agreement was drawn up between both parties to facilitate 

 the tracing and marking of the line by working conjointly. 



From the junction to Sonoyta, a Mexican and Indian rancheria, or village, situated near the 

 middle of the line, two roads run. The first one, which we will now describe, crosses the desert 

 west of the Sierra de la Gila, in a southeast direction, to a pass through one of its ridges leading 

 to water-holes, called by the xMexicans, " Tinajas Altas." These are natural wells formed in 

 the gullies, or arroyos, on the sides of the mountains, by dams composed of fragments of rocks 

 and sand washed down by heavy rains ; they are^filled up during the rainy seasons, and 

 frequently furnish travellers with water for many months of the year, being, in fact, their only 

 dependence. There are eight of these tinajas, one above the other, the highest two extremely 

 difficult to reach ; as the water is used from the lower ones you ascend to the next higher, pass- 

 ing it down by means of buckets. It is dangerous to attempt the highest, as it requires a skil- 

 ful climber to ascend the mountain, which is of granitic origin, the rocks smooth and slippery. 

 Although no vegetation marks the place, still it is readily found. A variety of birds frequent 

 the spot, principally the small, delicate humming-bird. The "palo de fierro" and the "palo 

 verde" grow near the base of the mountain. 



The distance to the ''Tinajas" is forty-five miles, over the desert plain already described ; 

 the first twelve through the heaviest kind of white sand, and it is next to an impossibility 

 for a train to pass over it, even by doubling teams— twelve mules to each wagon. Sixteen miles 

 and a half further on you reach the " Tinajas del Tule," situated in the mountains of the same 

 name, called so from tlie few scattered blades of coarse grass growing in their vicinity. The 

 water here is found in an arroyo, walled in by huge high masses of granitic rocks, which present 

 a peculiar appearance, as they lie in smooth whitish lumps huddled together in every possible 

 way. The road winds through the ridges of this sierra for many miles^ and then passes over a 

 plain in an easterly course until it turns the southern base of the " Cerro Salado." From this 

 point it follows up the valley of a subterraneous creek, (at two points of which sweet, or slightly 



