In the summer of 1854, Willis had a call from his down-river neighbor, Washington Irving, and repaid it at Sunnyside in 1859, in company with J. P. Kennedy and Lieutenant Wise, the author of “Los Gringos,” who had both been passing a day or two with him at Idlewild. Irving drove them through Sleepy Hollow, as recounted in “The Convalescent,” in which this visit fills an agreeable chapter; and Willis characteristically begged his host to give him his blotting-sheet for memorabilia, as being “the door-mat on which the thoughts of Irving’s last book had wiped their sandals as they went in.” “The Convalescent” (1859) was the last book which Willis published, if we except some late editions of his poems, but there are gleams in it, here and there, of the wit and fancy that never quite forsook him. There was, for instance, a long and very dark covered bridge over Moodna Creek, which he always entered with dread, when on horseback, and which he described as giving “a promise of emergence to light on the other side, which required the faith of a gimlet.” Upon the whole, it would be a very difficult reader who should refuse to admit the plea which the author urges in behalf of books of “The Convalescent” kind. “I learned also, to my comfort, that Nature publishes some volumes with many leaves, which are not intended to be of any posthumous value--the white poplar not lasting three moonlight nights after it is cut down. Even with such speedy decay, however, it throws a pleasant shade while it flourishes; and so, white poplar literature, recognized as a class in literature, should have its brief summer of indulgence.” Willis found that his best medicine was horseback riding, and spent as many hours as he could in the saddle. His horses and dogs were a great source of amusement to him. One of his special pets was Cæsar, a superb Newfoundland, that had been with Dr. Kane on one of his Arctic voyages, and was afterwards presented to Willis. When it died its grave at Idlewild was marked by a marble slab, the gift of Brown, the famous Grace Church sexton, with an epitaph of his own composition. The slab was on exhibition for a time, in July, 1862, at Barnum’s museum, and the inscription on it ran as follows:-- CÆSAR, WHO MADE THE VOYAGE TO THE ARCTIC REGIONS WITH DR. KANE, AND WAS AFTERWARDS THE FAVORITE DOG OF THE CHILDREN OF IDLEWILD, LIES BURIED BENEATH THIS STONE. Died December 7, 1861, aged thirteen years. Thy master’s record of thy worth made thee of great renown, And caused this tribute to thy memory from Sexton Brown.