The name of _pitahaya_ is given to this cactus by the Californians; but that, according to Dr Engelmann, is a general name applied in Mexico and South America to all the large columnar cacti which bear an edible fruit. "We encamped in a grove of cacti of all kinds," writes Mr Emory on the 4th November; "amongst them the huge pitahaya, one of which was fifty feet high." The next day "we followed the Gila for six miles. The pitahaya and every other variety of cactus flourished in great luxuriance. The pitahaya, tall, erect, and columnar in its appearance, grew in every crevice from the base to the tops of the mountains, and in one place I saw it growing nearly to its full dimensions from a crevice not much broader than the back of my sabre. These extraordinary-looking plants seem to seek the wildest and most unfrequented places." Although the course of the Gila is nine degrees to the north of the tropics, the vegetation, as exhibited in a plate at page 112, has something very tropical in its gigantic luxuriance and strange character. The geological features of the country are of corresponding peculiarity. On the 8th November, the course of the expedition was traversed by "a seam of yellowish-coloured igneous rock, shooting up into irregular spires and turrets, one or two thousand feet in height. It ran at right angles to the river, and extended to the north and to the south, in a chain of mountains as far as the eye could reach. One of these towers was capped with a substance many hundred feet thick, disposed in horizontal strata of different colours, from deep red to light yellow." A sketch of this singular chain of natural spires and towers is annexed to Mr Emory's description by one of his companions. At this part of the journey, although beaver "sign" and tracks of game were seen, few animals made their appearance. On the 6th November, the only creatures observed were lizards, scorpions, and tarantulas. Five days after, however, Mr Emory secured a long-sought bird, an inhabitant of the mezquite tree, having indigo-blue plumage, with top knot and a long tail, and whose wings, when spread, exhibit a white ellipse. "Strolling over the hills alone," says Mr Emory, "in pursuit of seeds and geological specimens, my thoughts went back to the States; and when I turned from my momentary aberrations, I was struck most forcibly with the fact that not one object in the whole view, animal, vegetable, or mineral, had anything in common with the products of any State in the Union, with the single exception of the cotton-wood, which is found in the Western States, and seems to grow wherever water flows from the vertebral range of mountains of North America."