Cormac McCarthy’s Next Pilgrimage : THE CROSSING: Volume II of the Border Trilogy, <i> By Cormac McCarthy (Alfred A. Knopf: $23; 421 pp.)</i>

In the second part of Cormac McCarthy’s epic trilogy, as in the first, the border between the United States and Mexico plays the same role as the rabbit-hole and the looking-glass in Lewis Carroll’s two books of Alice. The young adventurers--McCarthy uses a pair--set out from a real though vividly charged Arizona and New Mexico, and cross into a world where realism, folklore, out-sized passions and gnomic myths swirl in stormy colors.

Here is the difference: What is remarkable in the Alices lies at the bottom of the hole and the far side of the mirror. McCarthy’s writing, powerful on this side of the border, frequently overpowers itself once it gets to Mexico. His imagination advances in conquistador mode, seeking the gold of Mexican rural traditions, manners, beliefs--and the very language itself--to adorn the dull tin-cannery of the modern American soul and the flatness of American speech. Like other tourists and invaders, he can make an illness out of a hunger. McCarthy writes as if feasting, only to have his lavishly nourished prose deteriorate, at times, into a literary equivalent of La Turista.

Like “All the Pretty Horses� (the first book of the trilogy), “The Crossing� sends two young ranch boys south of the border. The time is not long before World War II, when Arizona and New Mexico were crossed by trailer trucks and crisscrossed by men on horseback; and Mexico could be seen, from this side of the trucks, as the great dreaming past that the American Southwest was losing.

As in the previous book, the story has elements both of a picaresque adventure and a metaphysical pilgrimage. In “The Crossing,� in particular, we catch an occasional breeze from Don Quixote and Sancho Panza, crossing Castille with a lofty and wrong-headed purpose. Even more strongly, there are echoes of the Arthurian cycle. Billy and Boyd Parham, like Sir Gawain and Sir Perceval, engage in bloody and terrifying exploits that carry hints of a higher purpose, a Grail. McCarthy’s spirit is closer to the fabulous prophetics of the Celtic legend than to the melancholy comedy of the Spanish satire. Among his conspicuous gifts--their conspicuousness can be a defect--humor and skepticism play little part.

“The Crossing� is divided into three sections. In the first, Billy traps a she-wolf that has wandered across the border and is marauding among the cattle on his family’s ranch. Something in her fierceness and solitude--�the reckonless deep of loneliness that cored the world to its heart�--touches the boy. He takes her into Mexico to release her in the mountains. Instead, he is stopped by the police; his wolf is confiscated and taken to a hacienda to fight dogs in a ring. Billy shoots her to end the indignity, trades his gun for her corpse, takes it into the mountains and, after hardships, the quiet kindness of peasants and Native Americans, and an encounter with a sage or two, makes his way home.

Bandits have killed his parents and stolen the horses. Billy collects his younger brother Boyd, and they make their way back to Mexico. They find three of the horses, steal them back, and fight a succession of battles with the men who have acquired them. Boyd, skeptical and reluctant up to then, less skilled and favored than Billy, has come into his own. Recovering from a gunshot wound, he disappears with a young Mexican woman who has joined them. Billy, after more hardships and a long detour through the story of a wise blind man, returns once more to the United States.

Two years later he makes his last trip, this time searching for Boyd. He comes upon him first in a local ballad about a young American who came to find justice and was killed. Eventually he locates the body, and returns to New Mexico to bury Boyd on the family land. The book ends with Billy spending a night in a desert hovel in the company of a misshapen stray dog, and waking to a dawn that grows darker instead of lighter. It is a partial solar eclipse, perhaps, but it plays the role of the mists into which legends disappear so as never to end.

McCarthy is a strong writer and he can be a magical one. Like Hemingway and Faulkner he has forged an utterly individual style, an order of passions, tastes and values, and a way of looking at the world. Like them he has the virtues of his idiosyncrasy and the defects as well; though I find the virtues, real ones, smaller and the defects quite a bit larger.

There are splendid passages in “The Crossing.� In two scenes at the start, McCarthy could be Hemingway on fishing or Faulkner on hunting. In one, Billy and Boyd come upon a Native American hiding near the family ranch and the tension and veiled threat of the encounter are memorable; in the other, the art and ordeal of tracking and trapping a wolf are told with glistening authority. In general, the parts that take place in the United States are clean and powerful; so is anything that portrays work or horses; so are the voices of Billy and Boyd, laconic and dry no matter what they are going through. There is a splendid fight or two; and the painstaking work of a village doctor on the wounded Boyd is a masterpiece of evocative realism with a haunting touch of mystery. Suddenly in the doctor there is a glimpse of Arthur’s Merlin.

What is painfully weak is much of McCarthy’s portrayal and use of Mexico; and it is a very serious weakness. McCarthy’s problem is not insensibility or superficiality. On the contrary, he regards his Mexicans with such a passionate, penetrating and appropriating glance that he all but obliterates them. He understands them to the point of invisibility. He has understood them and now he creates them. And they fall into categories: wise and gnomic old men, warm and generous campesinos, knife-wielding bad guys, brave and life-enhancing women who supply meaningful helpings of tortillas and beans.

It is wrong to wish that, just once, they would serve Spaghetti-O’s. The point is that McCarthy gives them no room, within their categories, to be individuals. They are the human frieze against which the spiritual pilgrimage of Billy will be played, and against which he will hear the three allegorical lessons that are the book’s thematic heart. They are delivered ponderously by a former priest and by a blind man’s companion and, quite enchantingly--perhaps it is the book’s best sequence--by philosophical gypsies. The message to the purposeful and struggling young man is, essentially, to struggle and intend less and to contemplate more.

Of all McCarthy’s appropriations, though, the worst, as it was in “Horses,� is his voluminous use of Spanish, whole sentences and paragraphs at a time. It cheapens the English, it cheapens the Spanish. But even worse: His Spanish is largely unidiomatic, often awkward and scattered with glaring mistakes. It makes no sense if he is writing for people who don’t know Spanish; it makes less sense if he is writing for people who do.