by Knopf, $22.00. Mr. Merwin describes life in the high limestone country of southwestern France in three narratives that should probably be considered a poet’s observations and suppositions rather than fiction. One first meets a financially decrepit nobleman turned petty con man and scrounger of antiques from the many deserted houses in the area. The second piece is based on the author’s love of the countryside, his sense of its past, its present decay, and the small grudges and tensions arising from the poverty of its people. The third section, “Blackbird’s Summer,” combines elements from its predecessors and adds Blackbird, a character who becomes monumental without doing anything but go about his business as wine merchant, hotel owner, and kindly good citizen. It is an impressive achievement for an author to make a memorable character out of a man who does nothing at all remarkable..