LONDON.- The bicentenary of the birth of the legendary nineteenth-century writer, Charles Dickens is celebrated in a new display at the National Portrait Gallery. Portraits of the author, his family and influential contemporaries chart the progress of his life and examine the enduring legacy of the characters he created. The fifteen works in this case display include photographs, drawings and engravings ranging from the early period of the writers career to posthumous images of his characters showing the longevity of his literary creations. The earliest portrait on display is a romantic portrait in oils of Dickens, aged 26, by Daniel Maclise, showing the writer enjoying his first taste of fame. Two photographs by Herbert Watkins in 1858 mark the celebrity Dickens had obtained by the mid-nineteenth century as both a writer and as a public reader of his works. The writers wife of twenty-two years, Catherine, is repres