Robert Browning's friendship for Isabella Blagden was almost as remarkable as was his love for Elizabeth Barrett. After Elizabeth's death (June 1861), Browning went to England to educate their son, but he hoped eventually to return to Italy, principally so that he might be near his friend "Isa." He asked her to write to him once a month on the twelfth, promising to answer her letter on the nineteenth.

The fulfillment of this obligation resulted in a correspondence which is remarkable from the standpoint of continuity. Most collections of letters suffer from their fragmentary form;...