point on the Colorado is 32° 29' 44".45 north, and the longitude of same 114° 48′ 44′′.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 237.63565 English miles. The mean of eighty barometrical 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 meanderings of the river is 27.9 miles, making the mean fall of the river between 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. The azimuth of the line is 71° 19′ 23′′.18 southeast; its 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 Mexicans, "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, passing it down by means of buckets. It is dangerous to attempt the highest, as it requires a skilful 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 the 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

brackish, water can be had by digging) to an Indian village called Quitobaquita, fifty-four miles from "Tule." Midway between these two places is a low mezquite flat called "Las Playas,' containing charcos, or holes, which are filled during the rainy season with water.

The second road from the junction, known by the name of the "Cabeza Prieta" route, from passing near "Tinajas," in the mountain of that name, after continuing up the Gila for forty miles, leaves it and joins the first at "Las Playas." At Quitobaquita there are fine springs running for the greater part of the year.

The road continues along the course of the subterraneous stream until you reach the Rancho de Sonoyta, thirteen miles and a half further on. From the junction to within a short distance of this place, a heavy road of one hundred and thirty miles, you look on a desert country. Near Sonoyta it is well covered with mezquite timber; in the valley, to the east of the town, there is some salt grass; but to the west, as far as the Colorado, scarce a blade is to be seen. A dull, wide waste lies before you, interspersed with low sierras and mounds, covered with black igneous rocks. The soil is a mixture of sand and gravel; the reflection from its white surface adds still greater torment to the intense and scorching heat of the sun. Well do I recollect the ride from Sonoyta to Fort Yuma and back, in the middle of August, 1855. It was the most dreary and tiresome I have ever experienced. Imagination cannot picture a more dreary, sterile country, and we named it the "Mal Pais." The burnt lime-like appearance of the soil is ever before you; the very stones look like the scoriæ of a furnace; there is no grass, and but a sickly vegetation, more unpleasant to the sight than the barren earth itself; scarce an animal to be seen-not even the wolf or the hare to attract the attention, and, save the lizard and the horned frog, naught to give life and animation to this region. The eye may watch in vain for the flight of a bird; to add to all is the knowledge that there is not one drop of water to be depended upon from Sonoyta to the Colorado or Gila. All traces of the road are sometimes erased by the high winds sweeping the unstable soil before them, but death has strewn a continuous line of bleached bones and withered carcases of horses and cattle, as monuments to mark the way.

Although I travelled over it with only four men in the most favorable time, during the rainy season of Sonora, our animals well rested and in good condition, still it was a difficult undertaking. On our way to the post from Sonoyta we met many emigrants returning from California, men and animals suffering from scarcity of water. Some men had died from thirst, and others were nearly exhausted. Among those we passed between the Colorado and the "Tinajas Altas,” was a party composed of one woman and three men, on foot, a pack-horse in wretched condition carrying their all. The men had given up from pure exhaustion and laid down to die; but the woman, animated by love and sympathy, had plodded on over the long road until she reached water, then clambering up the side of the mountain to the highest tinaja, she filled her bota, (a sort of leather flask,) and scarcely stopping to take rest, started back to resuscitate her dying companions. When we met them, she was striding along in advance of the men, animating them by her example.

On our return we had to ride to the "Tinajas Altas," forty-five miles, the first night to reach water; and the second one over sixty-three to "Agua Dulce," where we managed to obtain some by digging. During this time our poor mules plodded through the heavy sand without rest or food.

It was over this country one portion of the new boundary line was to be traced; the road

of which I have just spoken runs immediately along the line, and is the only practicable one connecting California and Sonora.

Before completing the work immediately on the river, a party had been sent out to make a reconnoissance in the direction of the line, and principally to examine the country for water. Anxious to have no delay, as the hot weather was fast coming on, and the river-bottom having become so infested with mosquitoes as to make life unendurable and labor of any kind impracticable, we commenced prolonging the line without awaiting the return of the reconnoitring party. Mr. Phillips, in the performance of this duty, reached the Tinajas, but there found very little water, and what there was, difficult of access; and, although directed to some new water-holes by a Papago Indian, still he only found sufficient to last a short time for a small number of men and animals. Mr. Alemán, of the Mexican commission, also endeavored to travel the road; but meeting the party first sent out, and hearing their report of the entire absence of water from the river to Sonoyta, was compelled to turn back.

The escort and provision train likewise made an attempt, but it was found almost impossible to advance more than a few miles with the heavily-loaded wagons. My own success was little better; starting from our camp with a light spring-wagon and six good mules, I managed to make twenty-five miles in twenty-eight hours' constant travel; an express then reached me from Mr. Alemán, informing me of the unfavorable account of the search for water.

Not finding it feasible to carry out our plan of operations, the parties of both commissions retraced their steps to the Gila. Every effort had been made to prosecute the work, under the most trying circumstances, but we found it useless to contend against impossibilities. It was then agreed by Mr. Jimenez and myself "to cease operations at the west end, and to proceed along the Gila to the east end of the azimuth line, there to fix the point of intersection of the parallel 31° 20′ north latitude with the 111th meridian west of Greenwich, and afterwards to trace the line from that point westward as far as practicable."

On May 5th both parties, American and Mexican, took the road leading up the Gila; this journey was a long and tedious one, our mules having been thoroughly used up in their service. on the desert. During the whole winter they had had but scanty grazing, and to find any at all had to be driven ten miles up the Gila. As there are but three or four families of whites living on the Colorado, and those only in charge of ferries, they did not pretend to cultivate the soil and raise grain; and at the post they had only sufficient for their own use. For some little barley, shipped at San Francisco and brought round by water, I paid twelve cents a pound, and for hay one hundred dollars per ton.

The condition of our animals compelled us to make but short marches each day, to enable them to recruit.

As the road we followed has been travelled and reported upon by others, I shall not dwell long upon the subject. It continues the greater part of the distance in the valley of the Gila, occasionally leaving it for a few miles to go upon the sand plains bordering the bottom-land, or where hills jut into the water's edge, such as "Los Metates," "Lomas Negras," or "Lomas del Muerto," either following round their bases or crossing them. The last named is really the only difficult place in the road, but a trying one for mules and wagons. It is 110 miles above Fort Yuma, and consists of steep, rugged buttes, which, in a low stage of the river, can be avoided by crossing to the other side, but in high water must be passed over. Here are several severe ascents and descents, one at an angle of forty-five degrees, where it is necessary to let wagons down by ropes; they are also covered with vesicular rocks, making them exceed