From Walcott, startling imagery; The Fortunate Traveller, by Derek Walcott. New York: Farrar, Straus, Giroux Inc. 99 pp. $11.95.

The clarity of Derek Walcott's imagery in this, his latest, volume of poems is often startling and impressive. These are the poems of a wanderer. They read like an autobiography; sometimes happy, sometimes sad.

In ''The Fortunate Traveller'' Walcott begins his travels in the Eastern United States, returns to his home in Trinidad, and then moves on to Wales and England. In each landscape he journeys from elation, to restless yearnings, to alienation.

Walcott captures the heartland of America, offering images that crystallize the commonplace. In ''Upstate'' he writes about a bus trip through the Catskills , ''where people live/ with the highway's flat certainty.'' He defines the American muse by combining Walker Evans's famous portrait of a tenant farmer's gaunt wife with the silent, stern strength of another rural woman.

A cosmopolitan, the poet strolls through Manhattan in ''Piano Practice.'' The poem closes with the distant sound of a street musician playing steel drums, ''the scales skittering like minnows across the sea.'' The poem closes with a strong image of the Caribbean -- integrating an island instrument with an island scene.

''North and South'' closes the first section of the book. In Virginia, Walcott writes, ''The ghosts of white-robed horsemen float through the trees,/ the galloping abhorrence of my race.'' The poet is an alien in this land.

The prodigal returns to Trinidad. In ''Map of the New World'' Walcott exposes the forces that shaped his world -- the heritage and promise he sometimes feels for the Caribbean, his education in classical literature, and his craving for other places.

Walcott writes several of the poems that immediately follow ''Map of the New World'' as a Caribbean bard. ''Hurucan'' testifies to the majesty and havoc of the islands' seasonal hurricanes with a primitive awe. ''Port of Spain'' portrays the city so clearly and with so much affection that it carries you there, ''where mournful tailors peer over old machines/ stitching June and July together seamlessly,/ and one waits for lightning as the armed sentry/ hopes in boredom for the crack of the rifle.''

It is worth being excited about this volume of poetry. Yet, as it moves to its conclusion, Walcott's circumstances and mood become increasingly bleak. His child is stillborn. He is divorced. The poetry suffers; images become less distinct. The protagonist of the title poem, a long one near the end of the book , is a bitter character whose movements are hard to follow.

One hopes that Walcott quickly moves beyond his hardships and finds a new muse.