Dulce, Tule, and Tinajas Altas, to mark the boundary. The line runs a few feet south of the springs at Quitobaquita, north of Agua Dulce and Agua Salada, and south of the Tinajas del Tule and Tinajas Altas. The sierras on which these two last are located were troublesome to work on; their summits are so peaked as to make it difficult to find a place sufficiently large upon which to stand or place an instrument. Those who visited these stations to determine them, had to console themselves by sitting up all night after their work was done, as there was not sufficient space to stretch themselves out. The big horn mountain goats frequent this region, and the noise of their horns as they butt them together in fight is often heard among the rocks. Mr. Schott has made a large and interesting collection of botanical plants and of natural history, besides making careful examinations of the geology of the country; he has also taken the views of the scenery along the line, which accompany this report. It was a happy day that witnessed the termination of the field-work. On the 25th of August both parties left Sonoyta for Altar, and thence via Santa Anna to Magdalena, in the State of Sonora. The tracing and marking and triangulation of the line having been completed, Mr. Jimenez and myself compared at this last place the data for fixing the respective distances. between stations, and the positions of the prominent topographical features of the country. The section marked "B," (see Astronomical and Geodetical work,) shows the results of calculations of the latitudes and longitudes of points in the triangulation made to determine the "azimuth line of twenty English miles," together with tables showing the lengths of iron rods, A and B, used for measuring the base line; tables for laying off the circumference of the circle having its centre at the junction of the Gila and Colorado, and radius of twenty miles; tabulation of results for the latitude of the initial point on the Colorado; astronomical determinations of positions on the azimuth line between the Colorado and 111th meridian; and distances between monuments. Tabulated distances along the routes in the neighborhood of the boundary line from the Pacific ocean to the Gulf of Mexico also accompany this report. At Imuris, a few miles from Magdalena, we found Lieutenant Patterson, encamped with the escort and train, having left Aribaca in August, and reached there via Tubac and Los Nogales. When at this last place, the Apaches, splendidly mounted upon fine horses, made a descent upon his animals and endeavored to stampede them. Although the Indians, in war-dress and uttering unearthly yells, dashed up within fifteen feet of the mules, then in excellent condition and well-rested, still their efforts were unsuccessful. At Imuris the parties of both commissions separated-the one to return to the city of Mexico, the other to cross the continent to the Gulf of Mexico, and thence to Washington city. I take great pleasure in reporting to the commissioner the very agreeable relations, both official and social, which constantly existed during a difficult work, with those gentlemen of the Mexican commission with whom we were so long and intimately associated. From Imuris we travelled the road up the San Ignacio river by Cocospera, a deserted mission, to the rancho de San Lazaro, where we struck the main southern emigrant road. If space permitted, I should like to dwell upon the rich valleys of the "Tierra Caliente" of Sonora, the towns. of Altar, Santa Anna, Magdalena, Imuris, San Ignacio, and Cocospera, through which we journeyed on our way home; upon their highly cultivated fields of grain and sugar-cane, irrigated by miles of acequias, and their gardens loaded with richly flavored fruit of the tropics as well as of the more temperate zones. At Magdalena we saw in the same garden, apples, peaches, apricots, pomegranates, figs, grapes, lemons and oranges. Leaving San Lazaro, we followed the road, via Santa Cruz, Janos, and Corralitos, to El Paso, and thence took the southern route through Texas to San Antonio de Bexar. From San Diego, on the Pacific ocean, via Fort Yuma, Tucson, Santa Cruz, Janos, El Paso, and San Antonio, to Indianola, on the Gulf of Mexico, measured by viameter, the distance is 1,727.32 miles. From San Diego, via Fort Yuma, Sonoyta, Altar, Imuris, Santa Cruz, Janos, El Paso, and San Antonio, to Indianola, the distance is 1,695.22 miles.* My party arrived at this place November 30, 1855; a few days after, it was discharged, and the property belonging to the commission disposed of by sales. I reached Washington January 10, 1856. To the officers of my escort, and to my assistants, I feel deeply indebted for their urbanity in all my companionship with them, and for their untiring efforts in the performance of their duties. I am, sir, very respectfully, your obedient servant, Major W. H. EMORY, U. S. Á., N. MICHLER, Lieut. Corps Top. Engineers, U. S. Army. U. S. Commissioner. RECONNOISSANCE TO THE MOUTH OF THE GILA RIVER, FROM SAN DIEGO, CALIFORNIA, SEPTEMBER 11 TO DECEMBER 10, 1849.--BY C. C. PARRY, M. D. On the 11th September, 1849, the astronomical party of the United States boundary commission, detailed by Major W. H. Emory for the determination of the point of junction of the Gila and Colorado rivers, left the Mission San Diego, en route across the mountains. A more direct course than that usually taken was concluded on, leading northeast by the Rancho Santa Monica, to intersect the road usually travelled at Santa Maria. Soon after leaving the mission grounds, we commence the ascent of the first rocky range, leading by steep slopes to a height of several hundred feet above the river valley; thence, passing over upland terraced plains, to descend a broken slope on the opposite (eastern) side. The rock exposures show a form of porphyritic greenstone, of close, compact texture, and uniform bluish color. As exposed in the line of the river course, which lies to our left, it exhibits abrupt broken walls, through which the river makes its way, forming, near its exit from the range, a distinct fall of ten or twelve feet in a distance of two hundred yards. At this point commences the line of irrigating ditch, which formerly supplied the cultivated grounds adjoining the Mission of San Diego, distant two miles or more. The only traces of this aqueduct now remaining consist of broken patches of masonry, seen at several points along the right bank of the stream. This greenstone range, having an average width of two to five miles, terminates on the east in an open basin valley, bounded on its western aspect by granite rocks, whose grey, mottled appearance shows a marked contrast to the uniform bluish aspect of the porphyry range. Our route thence, observing a general northeast course, passes diagonally over the wide basinvalley below, reaching, at a distance of twelve miles from the mission, the Rancho Santa Monica. This rancho occupies the left bank of the upper San Diego river, attached to which is a very considerable section of rich bottom-land, capable of irrigation. The higher lands, and mountain slopes adjoining, furnish the requisite pasture ground to extensive herds of cattle and * The distance can be shortened and the road improved by following the line of Lieutenant Parke's exploration through the new territory. W. H. E. horses. From this point, continuing a northeast course, the main stream of the San Diego river is crossed; thence you pass up a more northerly branch. On this route we soon approach an immense mountain wall, lying on our right, and blocking up our way eastward. The ascent of this was accomplished at a depressed point in the general range, leading by a rude, unbroken track along the edges of a ravine. The general height of the ridge, some eight hundred feet above the valley, was at last attained by doubling teams, and frequent manual assistance. Our route thence led along, and beyond, the line of broken valleys and irregular ridges, showing frequently depressed basins, over upland plains, to the Rancho Santa Maria. The rock exposure was quite uniform, being composed of crystalline feldspathic granite, coarsely grained, or showing occasionally a close sienitic texture. The computed height of the Rancho Santa Maria, above the sea, is 1,353 feet. It occupies the western edge of an extensive upland plain, from which is distinctly visible towards the east, at a distance of fifteen to twenty miles, the broken line of the dividing ridge of this mountain range. On the northern border of this plain lies the lower course of the Rio Santa Isabel, flowing hence in an irregular western course, and finally forming the San Diegito river, which empties into the ocean some twenty miles above San Diego. The open plain is destitute of timber, being covered mainly with pasture growth. The California live-oak (Quercus agrifolia) grows on all the adjoining mountain slopes. Continuing along the line of the main road to Santa Isabel, being the same followed by General Kearny in 1846, the day before the battle of San Pasqual, a gradually increasing elevation brings us in the midst of the attractive mountain scenery of this portion of California. We here pass amid groves of live-oak, verdant shrubbery, and rich pasturage, set off in the back-ground by high rocky cliffs, or disclosing, in the distance, pine-fringed heights, distinctly marked against the clear sky. At Santa Isabel we encounter a clear running stream, coursing through an open valley, surrounded by lofty mountains; those directly to the east form the dividing crest of the range. From this point there is a "cut-off" leading by a direct east course, over the mountain ridge, which rejoins the wagon road at San Felipe. To this route, being least known, we shall confine our remarks. Passing then directly up the main course of the Rio Santa Isabel, we follow a plain bridle-path, which, passing by frequent ascents, at first steep and broken, amid rocky exposures of granite, soon expands into quite an open valley. This valley is bounded on either side by steep mountains, along the sides of which, as we proceed upwards, pines make their appearance. Our trail, crossing from one side to another of the lively brook dignified with the title of the Rio Santa Isabel, brings us into the main road, about six miles above the settlements, and near the dividing crest of the main ridge. Just below this is situated the rancho of a Mr. Williams. The country here has a fresh mountain look; the air is cool and bracing. The rock exposures at this point show a form of quartz granite, frequently imbedding crystals of tourmaline. The view from the higher peaks in this vicinity, reaching probably a height of 5,000 feet or more above the sea, is strikingly grand. We here overlook, to the westward, the broken mountain ranges stretching in a dim line seaward; to the east the descent is more abrupt, and the view shows the bare outline of the desert mountains, projecting in irregular spurs into the desert plain, or standing as isolated ridges in the dull brown expanse below. The descent from the ridge to the east is by abrupt pitches along the sides of a steep ravine, opening out below into a dry waterless valley; this valley, thence expanding, forms the open plain of San Felipe, surrounded by dull ashy-colored mountains. The distance, by this pass, from Santa Isabel to San Felipe, is twelve miles, while the wagon road between these two points is twenty-five miles, or more, in length. The geological formation exhibited along the eastern slope of the mountain range at this point shows a very sensible change, and in place of the usual forms of feldspathic or quartz granite we meet with a more prevalent character of micaceous granite, in which the scales of mica are frequently of large size, and very confusedly intermixed. With this also occur mica and talcose slates, traversed by quartz veins. At this point, then, we have an approach to the gold formation, and in the section of country thus limited, exist the fairest prospects of mineral discoveries. The country thus characterized is, however, barren and desolate in the extreme; water is scarce, and pasturage of the poorest description. Thorny cacti and arid shrubbery usurp the soil, not only of the mountain clefts, but also of the open valleys. At this point, indeed, we may say, the desert proper commences; for it is here we have the first appearance of the desert plants Larrea Mexicana and Fouquiera Splendens. On leaving the last rocky exposures to enter on the open desert plain, we pass some distance down the bed of Cariso creek; along the course of which are exposed the high bluffs of sand, marl, and clay, exhibiting a fine sectional view of the tertiary formation on which the desert plateau is based. At the point where the road leaves the bed of the creek, to mount to the desert table-land, some 150 feet above, fossil marine shells of Ostrea are found, and gypsum makes its appearance in extensive beds. The upper layer of the table-land shows a variable thickness, composed of water-worn pebbles, derived from the adjoining mountains. Near the mountain base, this plateau has a height of about 500 feet above the level of the Colorado river. The surface extends in a gentle slope towards the Colorado, or eastward, about the distance of twenty-five miles, where it reaches its lowest depression at the Lagoon or "New river" basin, which is in fact a part of the extended alluvial tracts belonging to the Colorado river. The proof of this latter fact is seen in the barometric observations, showing a depression at this point, below the level of the Colorado river in high water, and also by tracing a direct connexion between the overflow of this latter stream and the appearance of water at New river. The numerous depressions found along the course of this alluvial tract have, moreover, all the character of the sedimentary soil of the Colorado bottoms, supporting, though more sparsely, the same character of vegetation, and showing, frequently, fluviatic shells, identical with those now found at lagoons and sloughs adjoining the river. This "New river" tract also receives the drainage of a large scope of desert country, which is sometimes visited by heavy showers of rain. It retains this rain-water, and river overflows, for several months; when both these sources fail, it becomes a perfectly dry bed, or contracts into quaggy saline marshes. When we stopped here, in the latter part of September, copious local rains had filled these lake reservoirs, which, with previous extensive river overflows, had enriched the soil and caused a rank growth of annual grama grass. This afforded a fine grazing camp for our animals for two months. Directly south from our camp at this place, and about eight miles distant, lies a high mountain range, having a direction nearly east and west. To the western and most prominent point of this range the name of "Signal Mountain" was given. This range is made up of a form of sienitic rock, associated with recent lava. Its surface is bare, and presents a forbidding outline of dark weathered rock, variously marked by furrows, and shows an irregular crest, gradually sloping towards the east. Our route hence to the Colorado river leaves this depressed alluvial tract to the south, and passes again over the hard, gravelly surface of the desert table-land till we come upon the regular wooded bottoms of the main river. These bottom-grounds are everywhere bounded by E. Layers of pebbles, 15 to 20 feet, corresponding to calcareous conglomerate forming the table-lands of the desert. Line of low-water mark. Natural Section. East bank of the Colorado river below mouth of the Gila river. Length 600 yards. F. Line of high-water mark, 12 feet above G. a distinct line of the desert table-land, which forms bluffs of greater or less height. The character of these bluffs is often obscured by drifting sand, which is constantly encroaching on the lower tracts. This upper bottom-land is densely wooded with mezquite, which here finds its most congenial soil, and spreads its thorny branches on all sides, forming impenetrable thickets. To this higher level succeeds a lower surface of moist soil, supporting cotton-wood and willow, both of which extend to the immediate edges of the stream. In passing up the river on its right bank to the junction of the Gila, we encounter a rocky ridge abutting directly on the river bank; thence rising inland into high rugged peaks, it forms the "Pilot Knob” range. The character of the rock, as exposed on the river bank, is gneiss, having a distinct laminated structure. This character gradually passes into a form of sienite, composing the principal mass of the adjoining mountain ridge. The immediate junction of the Gila and Colorado rivers is marked by a formation different from any elsewhere noticed. It consists of rounded knolls, which rise from fifty to one hundred and fifty feet above the river level, and are strewn over with the erratic deposites belonging to the desert formation. Its internal structure is thus in a great measure concealed. In the cleft made by the passage of the Colorado, just below the junction, the central nucleus is brought to view, and exhibits a form of epidote rock, occurring as an irregular breccia, and showing evidence of internal disturbance below. The Colorado river, below the junction, is barely five hundred feet across. The Gila, near its mouth, is one hundred and fifty feet wide. The depth of channel in each is very variable. The alluvial delta lying north of the junction of these two rivers is considerably below high-water mark. It thus furnishes soil suitable for cultivation, and is occupied as such by the Yumas Indians. Some two miles above the junction, on the right bank of the Colorado, are marks of an old river bed, which, in the time of floods, is filled with an obstructed body of water, forming frequent sloughs and lagoons along its course. The |